0001437749-24-027213 | 10-Q | XBRL Viewer

Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]

1. Description of the Business

Pulse Biosciences, Inc. is a novel bioelectric medicine company committed to health innovation using its patented Nano-pulse Stimulation ("NPS") technology, a revolutionary energy modality that delivers nanosecond-duration pulses of electrical energy, each less than a millionth of a second long, to non-thermally clear targeted cells while sparing adjacent noncellular materials. NPS technology, also referred to as Nanosecond Pulsed-Field Ablation ("nsPFA") technology when used to ablate cellular tissue, can be used to treat a variety of medical conditions for which an optimal solution remains unfulfilled. The Company developed its proprietary CellFX System, a novel nsPFA delivery platform, and commercialized the initial application of its nsPFA technology to treat benign lesions of the skin. In parallel, the Company has designed a variety of applicators, or disposables, to explore the potential use of the CellFX platform to treat disorders in other medical specialties, such as cardiology, gastroenterology, gynecology, and ear, nose and throat. These applicators include devices for open surgical procedures, endoscopic or minimally invasive procedures, and endoluminal catheters, and each has been used in preclinical studies. Based on our preclinical experience and the potential to significantly improve outcomes for patients in a large and growing market, the Company decided in 2022 to focus its primary efforts on the use of nsPFA energy and the CellFX platform in the treatment of atrial fibrillation ("AF") and in a select few other markets where it could have a profound positive impact on healthcare for both patients and providers, such as soft tissue ablation.

The Company was incorporated in Nevada on May 19, 2014. On June 18, 2018, the Company reincorporated from the State of Nevada to the State of Delaware. The Company is located in Miami, Florida, and continues to maintain its offices in Hayward, California. The Company maintains a website at www.pulsebiosciences.com where general information about the Company is available.

The Company’s activities are subject to significant risks and uncertainties, including the need for additional capital. The Company does not currently have any material cash flows from operations. It has had minimal revenue and currently generates no revenue and will need to raise additional capital to finance its operations. However, there can be no assurances that the Company will be able to obtain additional financing on acceptable terms and in the amounts necessary to fully fund its operating requirements.

Note 4 - Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Property and equipment, gross	$ 5,054	$ 5,004
Less: Accumulated depreciation and amortization	(3,741)	(3,476)
Total property and equipment, net	1,313	1,528
Leasehold Improvements [Member]
Property and equipment, gross	2,519	2,519
Laboratory Equipment [Member]
Property and equipment, gross	1,281	1,247
Furniture and Fixtures [Member]
Property and equipment, gross	966	966
Software and Software Development Costs [Member]
Property and equipment, gross	272	272
Construction in Progress [Member]
Property and equipment, gross	$ 16	$ 0

Note 8 - Commitments and Contingencies - Information Related to Right-of-use Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Right-of-use assets	$ 6,818		$ 7,256
Current operating lease liabilities	1,146		1,058
Non-current operating lease liabilities	7,497		8,086
Total lease liabilities	8,643		$ 9,144
Cash paid for operating lease liabilities	940	$ 907
2024 (remaining 6 months)	970
2025	1,977
2026	2,046
2027	2,117
Thereafter	4,074
Total lease payments	11,184
Less imputed interest	$ (2,541)
Weighted-average remaining lease term (Year)	5 years 4 months 2 days
Weighted-average discount rate	10.00%

Note 4 - Balance Sheet Components (Tables)

6 Months Ended

Jun. 30, 2024

Property, Plant and Equipment [Table Text Block]

	*June 30,*			*December 31,*
	*2024*			*2023*
Leasehold improvements	$	2,519		$	2,519
Laboratory equipment		1,281			1,247
Furniture, fixtures and equipment		966			966
Software		272			272
Construction in progress		16			—
Total property and equipment		5,054			5,004
Less: Accumulated depreciation and amortization		(3,741	)		(3,476	)
Total property and equipment, net	$	1,313		$	1,528

Schedule of Finite-Lived Intangible Assets [Table Text Block]

	*June 30,*			*December 31,*
	*2024*			*2023*
Acquired patents and licenses	$	7,985		$	7,985
Less: Accumulated amortization		(6,432	)		(6,099	)
Total intangible assets, net	$	1,553		$	1,886

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]

Years ending December 31:
2024 (remaining 6 months)	$	332
2025		665
2026		556
Total	$	1,553

Schedule of Accrued Liabilities [Table Text Block]

	*June 30,*		*December 31,*
	*2024*		*2023*
Compensation expense	$	2,678	$	3,199
Clinical trial fees and costs		10		84
Professional fees		324		343
Other		167		188
Total accrued expenses	$	3,179	$	3,814

Note 6 - Stockholders' Equity and Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Research and development		1,001		518		1,950		776
General and administrative		1,051		625		1,861		1,263
Total stock-based compensation expense	$	2,052	$	1,143	$	3,811	$	2,039

Share-Based Payment Arrangement, Cost by Plan [Table Text Block]

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Time-based options	$	1,315	$	876	$	2,478	$	1,554
Performance-based options		14		87		22		204
Market-based options		683		158		1,190		158
ESPP		40		22		121		123
Total stock-based compensation expense	$	2,052	$	1,143	$	3,811	$	2,039

Share-Based Payment Arrangement, Option [Member]

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Expected term in years		5.3 - 6.3		5.0 - 6.3		5.3 - 6.3		5.0 - 6.3
Expected volatility		91% - 95%		89% - 94%		91% - 95%		89% - 94%
Risk-free interest rate		4.1%		3.8%		4.0% - 4.5%		3.8%
Dividend yield		—		—		—		—

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Expected term in years		3.7 - 5.8		4.4 - 5.9		3.7 - 5.8		4.4 - 5.9
Expected volatility		90%		90%		90%		90%
Risk-free interest rate		4.4%		3.4%		4.2 - 4.4%		3.4%
Dividend yield		—		—		—		—

Market-based Options [Member]

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	*Stock Options Outstanding*
	*Number of shares*		*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		2,100,000	$	6.78		9.44
Options granted		800,000		7.68
Options exercised		—		—
Options canceled		—		—
Options expired		—		—
Balances — June 30, 2024		2,900,000	$	7.03		9.19
Exercisable — June 30, 2024		—		—		—

Performance Options [Member]

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		1,224,130		$	5.51		8.53
Options granted		39,000			8.44
Options exercised		(4,000	)		2.92
Options canceled		(3,000	)		2.92
Options expired		(1,000	)		2.92
Balances — June 30, 2024		1,255,130		$	5.62		8.10
Exercisable — June 30, 2024		438,628		$	7.63		7.26

Time-based Options [Member]

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		6,141,906		$	10.48		7.07
Options granted		1,316,143			8.66
Options exercised		(2,000	)		4.95
Options canceled		(6,542	)		20.82
Options expired		(7,875	)		15.49
Balances — June 30, 2024		7,441,632		$	10.14		7.04
Exercisable — June 30, 2024		3,696,439		$	14.11		4.81

The 2017 Employee Stock Purchase Plan [Member]

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Expected term in years		0.5 - 1.0		0.5 - 1.0		0.5 - 1.0		0.5 - 1.0
Expected volatility		98%		83%		98%		83%
Risk-free interest rate		4.9% - 5.3%		5.1% - 5.2%		4.9% - 5.3%		5.1% - 5.2%
Dividend yield		—		—		—		—

The 2015 Plan, 2017 Plan and Inducement Plan [Member]

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		9,466,036		$	9.01		7.78
Options granted		2,155,143			8.29
Options exercised		(6,000	)		3.60
Options canceled		(9,542	)		15.19
Options expired		(8,875	)		14.07
Balances — June 30, 2024		11,596,762		$	8.87		7.69
Exercisable — June 30, 2024		4,135,067		$	13.43		5.07

Note 6 - Stockholders' Equity and Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended				3 Months Ended	6 Months Ended			12 Months Ended
	Mar. 28, 2024	Apr. 30, 2023	Jan. 01, 2023	Jun. 09, 2022	Mar. 31, 2024	Dec. 31, 2023	May 31, 2021	Nov. 30, 2017	Jun. 30, 2024	Jun. 30, 2024	Jun. 30, 2023	Jun. 15, 2023	Dec. 31, 2023	Dec. 31, 2017	Sep. 30, 2023
Common Stock, Par or Stated Value Per Share (in dollars per share)						$ 0.001			$ 0.001	$ 0.001			$ 0.001
Equity Classified Subscription, Value									$ 47,700	$ 47,700
Right Offering Deemed Dividend									$ 47,700	47,700	$ 0
Proceeds from Warrant Exercises										0	$ 14,835
Time-based Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value										$ 8,800
Time-based Options [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage										25.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)										1 year
Performance-based Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value										$ 300
Market-based Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value										$ 4,600
The 2017 Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)														10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)														1,500,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)			1,200,000			1,375,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Number of Shares (in shares)														1,200,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Percent														4.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)									707,407	707,407
The 2017 Inducement Equity Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)								10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)								1,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)					2,000,000		1,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)									1,849,126	1,849,126
The 2017 Inducement Equity Incentive Plan [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage								25.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)								1 year
The 2017 Inducement Equity Incentive Plan [Member] \| Share-Based Payment Arrangement, Option [Member] \| Maximum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)								10 years
The 2017 Employee Stock Purchase Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)														250,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Number of Shares (in shares)									450,000	450,000				450,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Percent														1.50%
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)									485,359	485,359
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)										77,959
Loan Agreement [Member]
Debt Instrument, Decrease, Forgiveness		$ 65,000
Warrants Issued in 2024 Rights Offering [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)	0.5
Rights Offering Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)				1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 2.05		$ 2.05							$ 2.05
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)						7,317,072							7,317,072
Class of Warrants or Rights, Redemption Price Per Share (in dollars per share)						$ 0.01							$ 0.01
Class of Warrant or Right, Period of Written Notice for Exercise (Day)													30 days
Class of Warrant or Right, Percentage Required for Redemption						200.00%							200.00%
Class of Warrant or Right, Exercise, Consecutive Trading Days (Day)													20 days
Class of Warrant or Right, Exercised During Period (in shares)												7,250,897	66,175
Proceeds from Warrant Exercises												$ 14,900
Class of Warrant or Right, Outstanding (in shares)															0
The 2024 Right Offering [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.001
Equity Offering, Units, Maximum Amount Authorized (in shares)	6,000,000
Equity Offering Units, Offering Value	$ 60,000
Shares Issued, Price Per Share (in dollars per share)	$ 10
Number of Shares Per Unit Issued (in shares)	1
Number of Warrants in Each Unit (in shares)	2
Share Price (in dollars per share)	$ 11.55
Equity Classified Subscription, Value	$ 47,700
Right Offering Deemed Dividend	$ 47,700
Private Placement [Member] \| Robert W. Duggan [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001
Shares Issued, Price Per Share (in dollars per share)		$ 6.51
Stock Issued During Period, Shares, New Issues (in shares)		10,022,937
Rights Offering [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)				0.001
Shares Issued, Price Per Share (in dollars per share)				$ 2.05
Number of Shares Per Unit Issued (in shares)				1
Stock Issued During Period, Shares, New Issues (in shares)				7,317,072
Equity Offering, Units, Sale of Units (in shares)				7,317,072
Number of Warrants Per Unit (in shares)				1
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				7,317,072
Proceeds from Issuance of Common Stock				$ 15,000
Class of Warrants or Rights, Redemption Price Per Share (in dollars per share)				$ 0.01
Rights Offering [Member] \| Board of Directors Chairman [Member]
Investment Owned, Percent of Net Assets				56.00%

Note 6 - Stockholders' Equity and Stock-based Compensation - Option Assumptions (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Time-based and Performance Options [Member]
Risk-free interest rate	4.10%	3.80%		3.80%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Market-based Options [Member]
Expected volatility	90.00%	90.00%	90.00%	90.00%
Risk-free interest rate	4.40%	3.40%		3.40%
Minimum [Member] \| Time-based and Performance Options [Member]
Expected term in years (Year)	5 years 3 months 18 days	5 years	5 years 3 months 18 days	5 years
Expected volatility	91.00%	89.00%	91.00%	89.00%
Risk-free interest rate			4.00%
Minimum [Member] \| Market-based Options [Member]
Expected term in years (Year)	3 years 8 months 12 days	4 years 4 months 24 days	3 years 8 months 12 days	4 years 4 months 24 days
Risk-free interest rate			4.20%
Maximum [Member] \| Time-based and Performance Options [Member]
Expected term in years (Year)	6 years 3 months 18 days	6 years 3 months 18 days	6 years 3 months 18 days	6 years 3 months 18 days
Expected volatility	95.00%	94.00%	95.00%	94.00%
Risk-free interest rate			4.50%
Maximum [Member] \| Market-based Options [Member]
Expected term in years (Year)	5 years 9 months 18 days	5 years 10 months 24 days	5 years 9 months 18 days	5 years 10 months 24 days
Risk-free interest rate			4.40%

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023
Private Placement [Member]
Issuance cost	$ 6	$ 6
Shares Issued Upon Warrants Exercised [Member]
Issuance cost	$ 10
Issuance cost		$ 10

Note 3 - Investments and Fair Value of Financial Instruments - Financial Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Total assets measured at fair value	$ 23,608	$ 41,184
Fair Value, Inputs, Level 1 [Member]
Total assets measured at fair value	23,608	41,184
Fair Value, Inputs, Level 2 [Member]
Total assets measured at fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Total assets measured at fair value	0	0
Money Market Funds [Member]
Cash and Cash equivalents	23,608	41,184
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and Cash equivalents	23,608	41,184
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash and Cash equivalents	0	0
Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Cash and Cash equivalents	$ 0	$ 0

Note 7 - Research Grants and Agreements (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Research and Development Expense	$ 7,230	$ 6,697	$ 13,971	$ 12,526
Old Dominion University Research Foundation [Member] \| Sponsored Research Agreement SRA [Member]
Research and Development Expense	$ 0	$ 0	$ 0	$ 0

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Time-based Option Activity (Details) - Time-based Options [Member]	6 Months Ended	12 Months Ended
	Jun. 30, 2024 $ / shares shares	Dec. 31, 2023 $ / shares shares
Options balances, number of shares (in shares) \| shares	6,141,906
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 10.48
Options balances, weighted average remaining life (Year)	7 years 14 days	7 years 25 days
Options granted, number of shares (in shares) \| shares	1,316,143
Options granted, weighted average exercise price (in dollars per share) \| $ / shares	$ 8.66
Options exercised, number of shares (in shares) \| shares	(2,000)
Options exercised, weighted average exercise price (in dollars per share) \| $ / shares	$ 4.95
Options canceled, number of shares (in shares) \| shares	(6,542)
Options canceled, weighted average exercise price (in dollars per share) \| $ / shares	$ 20.82
Options expired, number of shares (in shares) \| shares	(7,875)
Options expired, weighted average exercise price (in dollars per share) \| $ / shares	$ 15.49
Options balances, number of shares (in shares) \| shares	7,441,632	6,141,906
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 10.14	$ 10.48
Options exercisable, number of shares (in shares) \| shares	3,696,439
Options exercisable, weighted average exercise price (in dollars per share) \| $ / shares	$ 14.11
Options exercisable, weighted average remaining life (Year)	4 years 9 months 21 days

Document And Entity Information - shares	6 Months Ended
Document And Entity Information - shares	Jun. 30, 2024	Aug. 12, 2024
Document Information [Line Items]
Entity Central Index Key	0001625101
Entity Registrant Name	Pulse Biosciences, Inc.
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2024
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Document Transition Report	false
Entity File Number	001-34899
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5696597
Entity Address, Address Line One	601 Brickell Key Drive
Entity Address, City or Town	Miami
Entity Address, State or Province	FL
Entity Address, Postal Zip Code	33131
City Area Code	510
Local Phone Number	906-4600
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	PLSE
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		61,290,294

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenues:
Total revenues	$ 0	$ 0	$ 0	$ 0
Cost and expenses:
Research and development	7,230	6,697	13,971	12,526
General and administrative	4,496	3,530	8,370	7,263
Total cost and expenses	11,726	10,227	22,341	19,789
Loss from operations	(11,726)	(10,227)	(22,341)	(19,789)
Other income:
Interest income, net	343	317	821	78
Total other income	343	317	821	78
Loss from operations, before income taxes	(11,383)	(9,910)	(21,520)	(19,711)
Income tax benefit	0	0	0	0
Net loss	(11,383)	(9,910)	(21,520)	(19,711)
Comprehensive loss	$ (11,383)	$ (9,910)	$ (21,520)	$ (19,711)
Net loss per share:
Basic and diluted net loss per share (in dollars per share)	$ (0.2)	$ (0.22)	$ (0.38)	$ (0.46)
Weighted average shares used to compute net loss per common share — basic and diluted (in shares)	57,180	46,086	57,152	42,420

Note 3 - Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Text Block]

3. Fair Value of Financial Instruments

The authoritative guidance with respect to fair value established a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three levels, and requires that assets and liabilities carried at fair value be classified and disclosed in one of three categories, as presented below.

Level 1 - Observable inputs such as quoted prices in active markets for an identical asset or liability that the Company has the ability to access as of the measurement date. Financial assets and liabilities utilizing Level 1 inputs include money market funds.

Level 2 - Inputs, other than quoted prices included within Level 1, which are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. The Company did not classify any of its investments within Level 2 of the fair value hierarchy.

Level 3 - Unobservable inputs for which there is little or no market data for the asset or liability which requires the reporting entity to develop its own assumptions. The Company did not classify any of its investments within Level 3 of the fair value hierarchy.

The following table sets forth the fair value of the Company’s financial instruments measured on a recurring basis as of June 30, 2024 and December 31, 2023, respectively (in thousands):

		*June 30, 2024*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	23,608	$	—	$	—	$	23,608
Total assets measured at fair value		$	23,608	$	—	$	—	$	23,608

		*December 31, 2023*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	41,184	$	—	$	—	$	41,184
Total assets measured at fair value		$	41,184	$	—	$	—	$	41,184

The Company did not have any financial liabilities measured on a recurring basis as of June 30, 2024 or December 31, 2023.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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Note 3 - Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2024

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

		*June 30, 2024*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	23,608	$	—	$	—	$	23,608
Total assets measured at fair value		$	23,608	$	—	$	—	$	23,608

		*December 31, 2023*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	41,184	$	—	$	—	$	41,184
Total assets measured at fair value		$	41,184	$	—	$	—	$	41,184

Note 3 - Fair Value of Financial Instruments (Details Textual) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Impairment of Marketable Securities	$ 0	$ 0

Note 6 - Stockholders' Equity and Stock-based Compensation - Stock-based Compensation Expense by Recorded Location (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Total stock-based compensation expense	$ 2,052	$ 1,143	$ 3,811	$ 2,039
Research and Development Expense [Member]
Total stock-based compensation expense	1,001	518	1,950	776
General and Administrative Expense [Member]
Total stock-based compensation expense	$ 1,051	$ 625	$ 1,861	$ 1,263

Note 4 - Balance Sheet Components - Schedule of Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
2024 (remaining 6 months)	$ 332
2025	665
2026	556
Total	$ 1,553	$ 1,886

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Stock Option Activity (Details) - The 2015 Plan, 2017 Plan and Inducement Plan [Member]	6 Months Ended	12 Months Ended
	Jun. 30, 2024 $ / shares shares	Dec. 31, 2023 $ / shares shares
Options balances, number of shares (in shares) \| shares	9,466,036
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 9.01
Options balances, weighted average remaining life (Year)	7 years 8 months 8 days	7 years 9 months 10 days
Options granted, number of shares (in shares) \| shares	2,155,143
Options granted, weighted average exercise price (in dollars per share) \| $ / shares	$ 8.29
Options exercised, number of shares (in shares) \| shares	(6,000)
Options exercised, weighted average exercise price (in dollars per share) \| $ / shares	$ 3.6
Options canceled, number of shares (in shares) \| shares	(9,542)
Options canceled, weighted average exercise price (in dollars per share) \| $ / shares	$ 15.19
Options expired, number of shares (in shares) \| shares	(8,875)
Options expired, weighted average exercise price (in dollars per share) \| $ / shares	$ 14.07
Options balances, number of shares (in shares) \| shares	11,596,762	9,466,036
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 8.87	$ 9.01
Options exercisable, number of shares (in shares) \| shares	4,135,067
Options exercisable, weighted average exercise price (in dollars per share) \| $ / shares	$ 13.43
Options exercisable, weighted average remaining life (Year)	5 years 25 days

Note 9 - Segment Reporting (Details Textual)	6 Months Ended
Note 9 - Segment Reporting (Details Textual)	Jun. 30, 2024
Number of Reportable Segments	1

Note 6 - Stockholders' Equity and Stock-based Compensation

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Text Block]

6. Stockholders’ Equity and Stock-Based Compensation

Subscription Rights

On March 28, 2024, the Company announced that its Board of Directors ("Board") unanimously approved plans to initiate a rights offering, whereby the Company would distribute non-transferable subscription rights at no charge to all holders of the Company's common stock, par value $0.001 per share (the "Common Stock"), as of the close of business on a record date to be determined. On May 20, 2024, the Company announced that the Board had set May 31, 2024 as the record date (the "Record Date"). All holders of Common Stock as of the Record Date received non-transferable subscription rights to purchase up to an aggregate of six million units (the “2024 Units”) with an aggregate offering value of up to $60 million (the "2024 Rights Offering") at a price per 2024 Unit equal to the lesser of: (i) $10 (the “Initial Price”) and (ii) the volume weighted average price of the Common Stock for the ten trading day period through and including the expiration date, June 26, 2024 (the "Expiration Date"), of the Rights Offering (the “Alternate Price”). Each subscription right entitled the holder to purchase 0.10864186 2024 Units for each share of Common Stock owned as of the Record Date. Each 2024 Unit consisted of one share of Common Stock and two warrants, each being a warrant to purchase one-half of one share of Common Stock. The subscription rights were to expire and have no value if they were not exercised prior to the Expiration Date. The Company determined that the equity-classified subscription rights represents a pro-rata distribution issued to existing stockholders as of the Record Date, which is based on a purchase price of $10 per 2024 Unit as compared to (1) the price of $11.55 per one share of Common Stock on the Record Date, plus (2) the value of the warrants on the Record Date. The Company determined the fair value of the equity-classified subscription rights as of the Record Date, which involved the use of a Monte Carlo simulation to value the underlying warrants. The Monte Carlo simulation was based on certain significant unobservable inputs, such as a risk-free interest rate, stock price volatility, dividend yield, and expected term of the rights offering. The fair value of the equity-classified subscription rights was $47.7 million and was recorded in equity on the balance sheet as part of additional paid-in capital. The deemed pro-rata distribution to shareholders of $47.7 million was reflected as an offsetting reduction in additional paid-in capital. The Company is in an accumulated deficit position and has elected a policy of recognizing the deemed pro-rata distribution to shareholders as a reduction to additional paid-in capital rather than a further increase to its accumulated deficit. See Note 12 for further discussion of the 2024 Rights Offering.

Private Placement Securities Purchase Agreement

On April 30, 2023, the Company entered into a Securities Purchase Agreement with Robert W. Duggan, the Company’s majority stockholder and Executive Chairman, pursuant to which the Company agreed to issue and sell to Mr. Duggan 10,022,937 shares of the Company’s common stock, par value $0.001 per share, in a Private Placement, at a price per share of $6.51. The parties completed the Private Placement on May 9, 2023, after satisfying all pre-closing conditions, and the Company issued the full number of shares to Mr. Duggan. The shares were paid for through the cancellation of the principal sum of $65.0 million borrowed by the Company pursuant to the 2022 Loan Agreement (See Note 8), together with all accrued and unpaid interest outstanding owed at the time of closing.

2022 Rights Offering

On June 9, 2022, the Company completed a rights offering (the “2022 Rights Offering") resulting in the sale of 7,317,072 units (the “2022 Units”), at a price of $2.05 per 2022 Unit, with each 2022 Unit consisting of one share of the Company’s common stock, par value $0.001 per share, and one warrant (the “2022 Rights Offering Warrants”) to purchase one share of common stock at a price of $2.05 per share. The common stock and warrants comprising the 2022 Units separated upon the closing of the 2022 Rights Offering and were issued individually. 7,317,072 shares of common stock and warrants to acquire up to an additional 7,317,072 shares of common stock were issued in the 2022 Rights Offering. The Company received aggregate gross proceeds from the 2022 Rights Offering of $15 million. In May 2023, the Company delivered an irrevocable notice of redemption to warrant holders and, on June 16, 2023, it redeemed the last of the outstanding 2022 Rights Offering Warrants at a price of $0.01 per warrant share. See the Common Stock Warrants section below for further details. Robert W. Duggan, the Company’s majority stockholder and Executive Chairman, purchased approximately 56% of the shares offered through the 2022 Rights Offering.

Common Stock Warrants

In connection with the 2022 Rights Offering, the Company issued 2022 Rights Offering Warrants to purchase a total of 7,317,072 shares of its common stock at an exercise price of $2.05. The 2022 Rights Offering Warrants were subject to redemption by the Company for $0.01 per underlying share of common stock, on not less than 30 days written notice, if the volume weighted average price of the Company’s common stock equals or exceeds 200% of the exercise price for the warrants, subject to adjustment, per share, for 20 consecutive trading days, provided that the Company may not redeem the warrants prior to the date that is three months after the issuance date. On May 10, 2023, the Company issued a press release announcing that on May 9, 2023 the terms for warrant redemption had been met. Pursuant to the redemption, the Company redeemed 66,175 warrants on the redemption date, June 16, 2023. Prior to the redemption date, warrants to purchase 7,250,897 shares were exercised, generating approximately $14.9 million of total gross proceeds to the Company. As of June 30, 2024, there were no 2022 Rights Offering Warrants outstanding.

Equity Plans

2017 Equity Incentive Plan and 2017 Inducement Equity Incentive Plan

The Board previously adopted, and the Company’s stockholders approved, the Company’s 2017 Equity Incentive Plan (the “2017 Plan”).

The 2017 Plan has a 10-year term, and provides for the grant of stock options, stock appreciation rights, restricted stock, RSUs, performance units, and performance shares to employees, directors and consultants of the Company and any parent or subsidiary of the Company, as the Compensation Committee of the Board may determine. Subject to an annual evergreen increase and adjustment in the case of certain capitalization events, the Company initially reserved 1,500,000 shares of the Company’s common stock for issuance pursuant to awards under the 2017 Plan. In addition, shares remaining available under the Company’s 2015 Equity Incentive Plan, as amended (the “2015 Plan”), and shares reserved but not issued pursuant to outstanding equity awards that expire or terminate without being exercised or that are forfeited or repurchased by the Company will be added to the shares of common stock available for issuance under the 2017 Plan. The 2017 Plan is administered by the Board’s Compensation Committee. Effective at both January 1, 2024 and 2023, the number of shares of common stock available under the 2017 Plan increased by 1,200,000, respectively, pursuant to the evergreen provision of the 2017 Plan. Under the evergreen provision of the 2017 Plan, the share increase is determined based on the least of (i) 1,200,000 shares, (ii) 4% of the Company’s common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Board. Additionally, in December 2023, the number of shares of common stock available under the 2017 Plan increased by 1,375,000 shares as a result of a stockholder vote held at a special meeting of stockholders. As of June 30, 2024, 707,407 shares of common stock remained available for issuance under the 2017 Plan.

During November 2017, the Board adopted the 2017 Inducement Equity Incentive Plan (the “Inducement Plan”) and reserved 1,000,000 shares of the Company’s common stock for issuance pursuant to equity awards granted under the Inducement Plan. The Inducement Plan was adopted without stockholder approval.

The Inducement Plan has a 10-year term and provides for the grant of equity-based awards, including non-statutory stock options, RSUs, restricted stock, stock appreciation rights, performance shares and performance units, and its terms are substantially similar to the 2017 Plan, including with respect to treatment of equity awards in the event of a “merger” or “change in control” as defined under the Inducement Plan. Options issued under the Inducement Plan may have a term up to ten years and have variable vesting provisions. New hire grants generally vest 25% per year starting upon the first anniversary of the grant. Equity-based awards issued under the Inducement Plan are only issuable to individuals not previously engaged as employees or individuals returning to employment with the Company following a bona-fide period of non-employment. In May 2021, the Board approved an amendment to the Inducement Plan to reserve an additional 1,000,000 shares of the Company’s common stock for issuance pursuant to the Inducement Plan. And, in March 2024, the Board approved a second amendment to the Inducement Plan to reserve an additional 2,000,000 shares of the Company’s common stock for issuance pursuant to the Inducement Plan. As of June 30, 2024, 1,849,126 shares of common stock remained available for issuance under the Inducement Plan.

A summary of stock option activity under the 2015 Plan, 2017 Plan, and Inducement Plan for the six-months ended June 30, 2024 is presented below:

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		9,466,036		$	9.01		7.78
Options granted		2,155,143			8.29
Options exercised		(6,000	)		3.60
Options canceled		(9,542	)		15.19
Options expired		(8,875	)		14.07
Balances — June 30, 2024		11,596,762		$	8.87		7.69
Exercisable — June 30, 2024		4,135,067		$	13.43		5.07

Time-based Options

The Company awards time-based options which vest and become exercisable, subject to the individual’s continued employment or service through the applicable vesting date. Time-based options can have various vesting schedules, most commonly new hire grants which generally vest 25% per year starting upon the first anniversary of the grant.

A summary of the time-based stock option activity under the 2015 Plan, 2017 Plan and Inducement Plan for the six-months ended June 30, 2024 is presented below:

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		6,141,906		$	10.48		7.07
Options granted		1,316,143			8.66
Options exercised		(2,000	)		4.95
Options canceled		(6,542	)		20.82
Options expired		(7,875	)		15.49
Balances — June 30, 2024		7,441,632		$	10.14		7.04
Exercisable — June 30, 2024		3,696,439		$	14.11		4.81

The fair value of the time-based options granted during the six-month period ended June 30, 2024 was $8.8 million.

Performance-based Options

Certain stock options awarded by the Company contain performance conditions related to certain financial measures and achievements of strategic and operational milestones. Once a specific performance condition is fulfilled, the associated options will fully vest and become exercisable.

A summary of the performance-based option activity under the 2017 Plan and Inducement Plan for the six-months ended June 30, 2024 is presented below:

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		1,224,130		$	5.51		8.53
Options granted		39,000			8.44
Options exercised		(4,000	)		2.92
Options canceled		(3,000	)		2.92
Options expired		(1,000	)		2.92
Balances — June 30, 2024		1,255,130		$	5.62		8.10
Exercisable — June 30, 2024		438,628		$	7.63		7.26

The fair value of the performance-based options granted during the six-month period ended June 30, 2024 was $0.3 million.

Market-based Options

Certain stock options awarded by the Company contain market conditions related to achievement of certain market capitalization targets. The options will vest and become exercisable once the specific market capitalization targets are fulfilled.

A summary of the market-based option activity under the 2017 Plan for the six-months ended June 30, 2024 is presented below:

	*Stock Options Outstanding*
	*Number of shares*		*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2023		2,100,000	$	6.78		9.44
Options granted		800,000		7.68
Options exercised		—		—
Options canceled		—		—
Options expired		—		—
Balances — June 30, 2024		2,900,000	$	7.03		9.19
Exercisable — June 30, 2024		—		—		—

The fair value of the market-based options granted during the six-month period ended June 30, 2024 was $4.6 million.

The Company estimates the fair value of time-based and performance-based stock options on the grant date using the Black-Scholes option pricing model. The estimated fair value of these employee stock options is amortized on a straight-line basis over the requisite service period of the awards. The Company reviews, and when deemed appropriate, updates the assumptions used on a periodic basis. The fair value of time-based and performance-based stock options was estimated using the following weighted-average assumptions:

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Expected term in years		5.3 - 6.3		5.0 - 6.3		5.3 - 6.3		5.0 - 6.3
Expected volatility		91% - 95%		89% - 94%		91% - 95%		89% - 94%
Risk-free interest rate		4.1%		3.8%		4.0% - 4.5%		3.8%
Dividend yield		—		—		—		—

The Company estimates the fair value of market-based stock options on the grant date using a Monte Carlo simulation model. The estimated fair value of these employee stock options is amortized over the requisite service period for each tranche of the awards. The requisite service period is the service period derived from the Monte Carlo simulation model. If the market capitalization targets are met sooner than the derived service period, the Company will accelerate the recognition of stock-based compensation expense to reflect the cumulative expense associated with the vested shares. The fair value of market-based stock options was estimated using the following weighted-average assumptions:

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Expected term in years		3.7 - 5.8		4.4 - 5.9		3.7 - 5.8		4.4 - 5.9
Expected volatility		90%		90%		90%		90%
Risk-free interest rate		4.4%		3.4%		4.2 - 4.4%		3.4%
Dividend yield		—		—		—		—

2017 Employee Stock Purchase Plan

The Board previously adopted, and the Company's stockholders approved, the Company’s 2017 Employee Stock Purchase Plan (the “2017 ESPP”).

The 2017 ESPP is a broad-based plan that provides employees of the Company and its designated affiliates with the opportunity to become stockholders through periodic payroll deductions that are applied towards the purchase of Company common shares at a discount from the then-current market price. Subject to adjustment in the case of certain capitalization events, a total of 250,000 common shares of the Company were available for purchase at adoption of the 2017 ESPP. Pursuant to the 2017 ESPP, the annual share increase pursuant to the evergreen provision is determined based on the least of (i) 450,000 shares, (ii) 1.5% of the Company’s common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Board. In 2024, the Company reserved an additional 450,000 shares under the 2017 ESPP pursuant to the evergreen provision. In 2023, the Board waived the evergreen provision and no additional shares were reserved under the 2017 ESPP. During the six months ended June 30, 2024, the Company issued 77,959 shares of common stock under the 2017 ESPP. As of June 30, 2024, 485,359 shares of common stock remained available for issuance under the 2017 ESPP.

The Company estimates the fair value of ESPP grants on their grant date using the Black-Scholes option pricing model. The estimated fair value of ESPP grants is amortized on a straight-line basis over the requisite service period of the grants. The Company reviews, and when deemed appropriate, updates the assumptions used on a periodic basis. The Company utilizes its estimated volatility in the Black-Scholes option pricing model to determine the fair value of ESPP grants. The fair value of ESPP grants was estimated using the following weighted-average assumptions:

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Expected term in years		0.5 - 1.0		0.5 - 1.0		0.5 - 1.0		0.5 - 1.0
Expected volatility		98%		83%		98%		83%
Risk-free interest rate		4.9% - 5.3%		5.1% - 5.2%		4.9% - 5.3%		5.1% - 5.2%
Dividend yield		—		—		—		—

Stock-based Compensation

Total stock-based compensation expense consisted of the following (in thousands):

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Research and development		1,001		518		1,950		776
General and administrative		1,051		625		1,861		1,263
Total stock-based compensation expense	$	2,052	$	1,143	$	3,811	$	2,039

As of June 30, 2024, not all of the performance conditions of the performance options are probable to be achieved. Compensation expense has only been recognized for those conditions that are assumed to be probable.

Total stock-based compensation expense by award type was as follows (in thousands):

	*Three Months Ended June 30,*				*Six Months Ended June 30,*
	*2024*		*2023*		*2024*		*2023*
Time-based options	$	1,315	$	876	$	2,478	$	1,554
Performance-based options		14		87		22		204
Market-based options		683		158		1,190		158
ESPP		40		22		121		123
Total stock-based compensation expense	$	2,052	$	1,143	$	3,811	$	2,039

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Private Placement [Member] Common Stock [Member]	Private Placement [Member] Additional Paid-in Capital [Member]	Private Placement [Member] AOCI Attributable to Parent [Member]	Private Placement [Member] Retained Earnings [Member]	Private Placement [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2022						37,235
Balance at Dec. 31, 2022						$ 37	$ 292,420	$ 0	$ (294,705)	$ (2,248)
Issuance of common stock upon exercise of stock options (in shares)						13
Issuance of common stock upon exercise of stock options						$ 0	58	0	0	58
Rights offering deemed pro-rata distribution to shareholders (Note 6)										0
Stock-based compensation expense						0	2,039	0	0	2,039
Net loss						$ 0	0	0	(19,711)	(19,711)
Issuance of shares under employee stock purchase plan (in shares)						262
Issuance of shares under employee stock purchase plan						$ 1	291	0	0	292
Issuance of common stock as part of debt extinguishment, net of issuance costs of $6 (in shares)	10,023
Issuance of common stock as part of debt extinguishment, net of issuance costs of $6	$ 10	$ 65,233	$ 0	$ 0	$ 65,243
Issuance of common stock pursuant to warrant exercise (in shares)						7,238
Issuance of common stock pursuant to warrant exercise						$ 7	14,820	0	0	14,827
Balance (in shares) at Jun. 30, 2023						54,771
Balance at Jun. 30, 2023						$ 55	374,861	0	(314,416)	60,500
Balance (in shares) at Mar. 31, 2023						37,593
Balance at Mar. 31, 2023						$ 38	293,801	0	(304,506)	(10,667)
Issuance of common stock upon exercise of stock options (in shares)						13
Issuance of common stock upon exercise of stock options						$ 0	58	0	0	58
Stock-based compensation expense						0	1,143	0	0	1,143
Net loss						$ 0	0	0	(9,910)	(9,910)
Issuance of common stock as part of debt extinguishment, net of issuance costs of $6 (in shares)	10,023
Issuance of common stock as part of debt extinguishment, net of issuance costs of $6	$ 10	$ 65,236	$ 0	$ 0	$ 65,246
Issuance of common stock pursuant to warrant exercise (in shares)						7,142
Issuance of common stock pursuant to warrant exercise						$ 7	14,623	0	0	14,630
Balance (in shares) at Jun. 30, 2023						54,771
Balance at Jun. 30, 2023						$ 55	374,861	0	(314,416)	60,500
Balance (in shares) at Dec. 31, 2023						55,144
Balance at Dec. 31, 2023						$ 55	381,220	0	(336,915)	44,360
Issuance of common stock upon exercise of stock options (in shares)						6
Issuance of common stock upon exercise of stock options						$ 0	22	0	0	22
Issuance of equity-classified subscription rights as part of rights offering (Note 6)						0	47,700	0	0	47,700
Rights offering deemed pro-rata distribution to shareholders (Note 6)						0	(47,700)	0	0	(47,700)
Stock-based compensation expense						0	3,811	0	0	3,811
Net loss						$ 0	0	0	(21,520)	(21,520)
Issuance of shares under employee stock purchase plan (in shares)						78
Issuance of shares under employee stock purchase plan						$ 0	296	0	0	296
Balance (in shares) at Jun. 30, 2024						55,228
Balance at Jun. 30, 2024						$ 55	385,349	0	(358,435)	26,969
Balance (in shares) at Mar. 31, 2024						55,225
Balance at Mar. 31, 2024						$ 55	383,284	0	(347,052)	36,287
Issuance of common stock upon exercise of stock options (in shares)						3
Issuance of common stock upon exercise of stock options						$ 0	13	0	0	13
Issuance of equity-classified subscription rights as part of rights offering (Note 6)						0	47,700	0	0	47,700
Rights offering deemed pro-rata distribution to shareholders (Note 6)						0	(47,700)	0	0	(47,700)
Stock-based compensation expense						0	2,052	0	0	2,052
Net loss						$ 0	0	0	(11,383)	(11,383)
Balance (in shares) at Jun. 30, 2024						55,228
Balance at Jun. 30, 2024						$ 55	$ 385,349	$ 0	$ (358,435)	$ 26,969

Note 4 - Balance Sheet Components - Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Compensation expense	$ 2,678	$ 3,199
Clinical trial fees and costs	10	84
Professional fees	324	343
Other	167	188
Total accrued expenses	$ 3,179	$ 3,814

Note 8 - Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2024

Schedule of Information Related to Right-of-use Assets and Lease Liabilities [Table Text Block]

	*June 30,*		*December 31,*
Assets:	*2024*		*2023*
Right-of-use assets	$	6,818	$	7,256

	*June 30,*		*December 31,*
Liabilities:	*2024*		*2023*
Current operating lease liabilities	$	1,146	$	1,058
Non-current operating lease liabilities		7,497		8,086
Total lease liabilities	$	8,643	$	9,144

	*Six Months Ended June 30,*
	*2024*		*2023*
Cash paid for operating lease liabilities	$	940	$	907

Year ending December 31:
2024 (remaining 6 months)	$	970
2025		1,977
2026		2,046
2027		2,117
Thereafter		4,074
Total lease payments		11,184
Less imputed interest		(2,541	)
Total lease liabilities	$	8,643

Weighted-average remaining lease term			5.34
Weighted-average discount rate			10	%

Note 2 - Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2024

Schedule of Product Warranty Liability [Table Text Block]

	*Three Months Ended June 30,*					*Six Months Ended June 30,*
	*2024*		*2023*			*2024*		*2023*
Beginning balance	$	—	$	50		$	—	$	50
Add: Accruals for warranties issued during the period		—		—			—		—
Less: Adjustment for inventory at cost and excessive and obsolete inventory		—		(50	)		—		(50	)
Ending balance	$	—	$	—		$	—	$	—

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	*Six Months Ended June 30,*
	*2024*		*2023*
Common stock options		11,596,762		6,888,015
Total		11,596,762		6,888,015

Note 12 - Subsequent Events

6 Months Ended

Jun. 30, 2024

Subsequent Events [Text Block]

12. Subsequent Events

On July 3, 2024, the Company announced the closing of its 2024 Rights Offering. The 2024 Rights Offering resulted in the sale of six million 2024 Units, at a price of $10.00 per 2024 Unit. Each 2024 Unit consisted of one share of the Company’s common stock, par value $0.001 per share, and two warrants, each being a warrant to purchase one-half of one share of common stock. The common stock and warrants comprising the 2024 Units separated upon the closing of the 2024 Rights Offering and were issued individually. A total of 5,999,999 shares of common stock and warrants to acquire up to an additional approximately six million shares of common stock were issued in the offering. The Company received aggregate gross proceeds from the 2024 Rights Offering of $60 million. If exercised, additional gross proceeds of up to $66 million may be received through the exercise of warrants issued in the 2024 Rights Offering. Each warrant will be exercisable for $11.00 per whole share, which equals 110% of the subscription price for the Units. Warrants are exercisable immediately and will expire on the fifth anniversary of the closing of the 2024 Rights Offering. Half of the warrants issued in the rights offering are redeemable by the Company if the Company’s stock trading price exceeds $16.50 for twenty consecutive trading days and the other half of the warrants issued in the rights offering are redeemable by the Company if its stock trading price exceeds $22.00 for twenty consecutive trading days. The shares issued included approximately five million shares in aggregate to Mr. Duggan and affiliates of his, which brings Mr. Duggan’s current beneficial ownership in the Company to approximately 73%.

Note 4 - Balance Sheet Components

6 Months Ended

Jun. 30, 2024

Supplemental Balance Sheet Disclosures [Text Block]

4. Balance Sheet Components

Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):

	*June 30,*			*December 31,*
	*2024*			*2023*
Leasehold improvements	$	2,519		$	2,519
Laboratory equipment		1,281			1,247
Furniture, fixtures and equipment		966			966
Software		272			272
Construction in progress		16			—
Total property and equipment		5,054			5,004
Less: Accumulated depreciation and amortization		(3,741	)		(3,476	)
Total property and equipment, net	$	1,313		$	1,528

Depreciation expense was $0.1 million for each of the three-month periods ended June 30, 2024 and 2023, and $0.3 million for each of the six-month periods ended June 30, 2024 and 2023, respectively.

Intangible Assets, Net

Intangible assets primarily consist of acquired licenses to utilize certain patents, know-how and technology relating to the Company’s NPS technology for biomedical applications acquired from Old Dominion University Research Foundation (“ODURF”), Eastern Virginia Medical School, and the University of Southern California. In addition, the Company entered into a Sponsored Research Agreement with Old Dominion University’s Frank Reidy Research Center for Bioelectrics, which includes certain intellectual property rights arising from the research. The Company is amortizing the intangible assets over an estimated useful life of 12 years.

Intangible assets, net consisted of the following (in thousands):

	*June 30,*			*December 31,*
	*2024*			*2023*
Acquired patents and licenses	$	7,985		$	7,985
Less: Accumulated amortization		(6,432	)		(6,099	)
Total intangible assets, net	$	1,553		$	1,886

A schedule of the amortization of intangible assets for the remainder of 2024 and the succeeding two fiscal years is as follows (in thousands):

Years ending December 31:
2024 (remaining 6 months)	$	332
2025		665
2026		556
Total	$	1,553

Accrued Expenses

Accrued expenses consisted of the following (in thousands):

	*June 30,*		*December 31,*
	*2024*		*2023*
Compensation expense	$	2,678	$	3,199
Clinical trial fees and costs		10		84
Professional fees		324		343
Other		167		188
Total accrued expenses	$	3,179	$	3,814

Note 2 - Summary of Significant Accounting Policies - Warrant Accrual Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Beginning balance	$ 0	$ 50	$ 0	$ 50
Add: Accruals for warranties issued during the period	0	0	0	0
Less: Adjustment for inventory at cost and excessive and obsolete inventory	0	(50)	0	(50)
Ending balance	$ 0	$ 0	$ 0	$ 0

Note 2 - Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Antidilutive securities (in shares)	11,596,762	6,888,015
Share-Based Payment Arrangement, Option [Member]
Antidilutive securities (in shares)	11,596,762	6,888,015

Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares shares in Thousands	Jun. 30, 2024	Dec. 31, 2023
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	50,000	50,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000	500,000
Common stock, shares issued (in shares)	55,228	55,144
Common stock, shares outstanding (in shares)	55,228	55,144

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Market-based Option Activity (Details) - Market-based Options [Member]	6 Months Ended	12 Months Ended
	Jun. 30, 2024 $ / shares shares	Dec. 31, 2023 $ / shares shares
Options balances, number of shares (in shares) \| shares	2,100,000
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 6.78
Options balances, weighted average remaining life (Year)	9 years 2 months 8 days	9 years 5 months 8 days
Options granted, number of shares (in shares) \| shares	800,000
Options granted, weighted average exercise price (in dollars per share) \| $ / shares	$ 7.68
Options exercised, number of shares (in shares) \| shares	0
Options exercised, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Options canceled, number of shares (in shares) \| shares	0
Options canceled, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Options expired, number of shares (in shares) \| shares	0
Options expired, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Options balances, number of shares (in shares) \| shares	2,900,000	2,100,000
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 7.03	$ 6.78
Options exercisable, number of shares (in shares) \| shares	0
Options exercisable, weighted average exercise price (in dollars per share) \| $ / shares	$ 0

Note 8 - Commitments and Contingencies (Details Textual) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 30, 2023 USD ($) $ / shares shares	Jun. 30, 2024 USD ($) $ / shares	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) $ / shares	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) $ / shares	Sep. 20, 2022 USD ($)	May 31, 2019 ft²	Jul. 31, 2017 ft²
Common Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares		$ 0.001		$ 0.001		$ 0.001
Operating Lease, Expense		$ 0.6	$ 0.5	$ 1.2	$ 1.0
Corporate Headquarters in Hayward, California [Member]
Lessee, Operating Lease, Term of Contract (Year)									5 years
Area of Real Estate Property (Square Foot) \| ft²									15,700
Corporate Headquarters in Hayward, California [Member] \| Expansion Premises 1 [Member]
Area of Real Estate Property (Square Foot) \| ft²								13,300
Corporate Headquarters in Hayward, California [Member] \| Expansion Premises 2 [Member]
Area of Real Estate Property (Square Foot) \| ft²								21,300
Robert W. Duggan [Member] \| Private Placement [Member]
Stock Issued During Period, Shares, New Issues (in shares) \| shares	10,022,937
Common Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares	$ 0.001
Shares Issued, Price Per Share (in dollars per share) \| $ / shares	$ 6.51
Two Thousand Twenty Two Loan Agreement [Member] \| Robert W. Duggan [Member]
Debt Instrument, Face Amount							$ 65.0
Debt Instrument Quarterly Interest Rate							5
Debt Instrument, Increase, Accrued Interest						$ 1.7
Interest Expense						$ 1.1
Loan Agreement [Member]
Debt Instrument, Decrease, Forgiveness	$ 65.0
Interest Payable	$ 0.2

Note 4 - Balance Sheet Components (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Depreciation	$ 100	$ 100	$ 264	$ 271
Finite-Lived Intangible Asset, Useful Life (Year)	12 years		12 years

Note 5 - Goodwill (Details Textual) $ in Thousands	6 Months Ended	12 Months Ended
Note 5 - Goodwill (Details Textual) $ in Thousands	Jun. 30, 2024 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2023 USD ($)
Goodwill, Ending Balance	$ 2,791		$ 2,791
Goodwill, Impairment Loss	$ 0
Series of Individually Immaterial Business Acquisitions [Member]
Number of Businesses Acquired		3
Business Combination, Consideration Transferred, Total		$ 5,500
Goodwill, Ending Balance		$ 2,800

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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Note 2 - Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2024

Significant Accounting Policies [Text Block]

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared on a basis consistent with the Company’s December 31, 2023 audited Consolidated Financial Statements and include all adjustments, consisting of only normal recurring adjustments, necessary to fairly state the information set forth herein. The condensed consolidated financial statements have been prepared in accordance with the applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) and, as permitted by such rules and regulations, omit certain information and footnote disclosures necessary to present the financial statements in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). The condensed consolidated balance sheet as of December 31, 2023 was derived from the audited consolidated financial statements as of that date but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. The results of operations for the three-month and six-month periods ended June 30, 2024, are not necessarily indicative of the results to be expected for the entire year or any future periods.

Principles of Consolidation

The accompanying condensed consolidated financial statements include the financial statements of Pulse Biosciences, Inc. and its wholly-owned subsidiaries. Intercompany balances and transactions, if any, have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates that affect the amounts reported in the financial statements and accompanying notes to the financial statements. Estimates include, but are not limited to, the valuation and recognition of stock-based compensation, the valuation of equity-classified subscription rights, inventory valuation, warranty obligations, income taxes, and the useful lives assigned to long-lived assets. The Company evaluates its estimates and assumptions based on historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ materially from these estimates.

Significant Accounting Policies

The Company’s significant accounting policies are described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. The Company continually evaluates the accounting policies and estimates used in preparing the consolidated financial statements. During both the year ended December 31, 2023, and the six-month period ended June 30, 2024, the Company issued stock options to certain employees which contain market conditions related to overall market capitalization. Additionally, the Company has issued stock options to certain employees which contain performance conditions related to certain financial measures and achievements of strategic and operational milestones.

Stock-Based Compensation

The Company's stock-based compensation programs include stock options and an employee stock purchase program.

The Company periodically issues stock options to officers, directors, employees, and consultants for services rendered. Such issuances vest and expire according to terms established at the issuance date. Stock-based payments to officers, directors and employees, including grants of employee stock options, are recognized in the financial statements based on their grant date fair values, which are estimated using the Black-Scholes option-pricing model. Stock-based compensation expense is charged to operations on a straight-line basis over the vesting period. The Company has granted stock options with both time-based as well as performance-based vesting conditions. For stock awards with performance-based vesting conditions, the Company does not recognize compensation expense until it is probable that the performance-based vesting condition will be achieved. The analysis to determine such probability involves estimates and judgements from management and the estimate of expense may be revised periodically.

The Company has also issued certain stock options with market-based vesting conditions. These vesting conditions relate to the achievement of certain market capitalization targets of the Company. The grant date fair value for these stock options was determined using a Monte Carlo simulation. The expense is recognized over the requisite service period for each tranche of the awards. The requisite service period is the service period derived from the Monte Carlo simulation model. If the market capitalization targets are met sooner than the derived service period, the Company will accelerate the recognition of stock-based compensation expense to reflect the cumulative expense associated with the vested shares. The Monte Carlo simulation requires the Company to make assumptions and judgements about the variables used in the calculation including the expected term, volatility of the Company's common stock, an assumed risk-free interest rate, and cost of equity. The assumptions used in the option-pricing model represent management’s best estimates. If factors change and different assumptions are used, the Company's stock-based compensation expense could be materially different in the future.

See Note 6 for a detailed discussion of the Company’s stock plans and stock-based compensation expense.

Product Warranty

The Company provides a standard warranty on eligible products which provides the customer assurances that the products comply with the agreed-upon specifications. The standard warranty does not provide any services in addition to those assurances. The Company accrued a warranty reserve for products sold based upon the best estimate of the nature, frequency, and costs of future claims. These estimates are inherently uncertain given the short history of sales, and changes to the historical or projected warranty experience may cause material changes to the warranty reserve in the future. In June 2023, the Company reduced the accrued warranty liability to zero. Based upon the Company's shift in focus, there are a limited number of consoles currently covered under the standard warranty. All inventory has been fully written off, therefore the only incremental costs to fulfill a warranty claim in 2024 would be shipping costs or the costs to replace the CellFX nsPFA electrode, which would be immaterial in nature.

Warranty accrual activity consisted of the following for the three-month and six-month periods ended June 30, 2024 and 2023 (in thousands):

	*Three Months Ended June 30,*					*Six Months Ended June 30,*
	*2024*		*2023*			*2024*		*2023*
Beginning balance	$	—	$	50		$	—	$	50
Add: Accruals for warranties issued during the period		—		—			—		—
Less: Adjustment for inventory at cost and excessive and obsolete inventory		—		(50	)		—		(50	)
Ending balance	$	—	$	—		$	—	$	—

Net Loss per Share

The Company calculates basic net loss per share by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by giving effect to all potential dilutive common stock equivalents outstanding during the period. For purposes of this calculation, options to purchase common stock and common stock warrants are considered common stock equivalents. Potential common shares that have an anti-dilutive effect (i.e., those that increase income per share or decrease loss per share) are excluded from the calculation of diluted net loss per share.

Based on the Accounting Standards Codification ("ASC") 260-10-55, Earnings Per Share - Implementation Guidance and Illustrations, the Company determined that the 2024 Rights Offering (Note 6), contained a bonus element. A rights offering is deemed to have a bonus element when the exercise price at issuance is less than fair value of the Company's stock. The Company has retroactively adjusted earnings per share and weighted average number of shares outstanding for the bonus element for all periods presented.

Basic and diluted net loss per common share is the same for all periods presented because all warrants, stock options and restricted stock units outstanding are anti-dilutive.

The following outstanding stock options, and warrants were excluded from the computation of diluted net loss per share for the periods presented because including them would have had an anti-dilutive effect:

	*Six Months Ended June 30,*
	*2024*		*2023*
Common stock options		11,596,762		6,888,015
Total		11,596,762		6,888,015

Recent Accounting Pronouncements Not Yet Adopted

In March 2024, the FASB issued ASU No. 2024-02, Codification Improvements - Amendments to Remove References to the Concepts Statements, an amendment of the FASB Accounting Standards Codification. The amendments in this ASU are related to the removal of various references to FASB Concept Statements from the codification to make clear distinctions between authoritative and non-authoritative literature in the codification. This ASU is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The Company does not believe this standard will have an impact on its consolidated financial statements and related disclosures.

As of June 30, 2024, there were no additional material changes to the information provided regarding recent accounting pronouncements in Note 2, “Summary of Significant Accounting Policies” in the Company’s Form 10-K for the fiscal year ended December 31, 2023.

Note 10 - Related Party Transactions (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	May 31, 2023	Apr. 30, 2023	Sep. 20, 2022	May 31, 2022	Jun. 30, 2024	Dec. 31, 2023
Accrued Liabilities, Current					$ 3,179	$ 3,814
Common Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001	$ 0.001
Loan Agreement [Member]
Debt Instrument, Decrease, Forgiveness		$ 65,000
Interest Payable		$ 200
Robert W. Duggan [Member] \| Private Placement [Member]
Stock Issued During Period, Shares, New Issues (in shares)		10,022,937
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001
Shares Issued, Price Per Share (in dollars per share)		$ 6.51
Letter Agreement [Member] \| Robert W. Duggan [Member]
Directors and Officers Liability Insurance, Period (Year)				1 year
Related Party Transaction, Amounts of Transaction	$ 1,000		$ 65,000
Accrued Liabilities, Current					$ 0

Insider Trading Arrangements	3 Months Ended	6 Months Ended
Insider Trading Arrangements	Jun. 30, 2024	Jun. 30, 2024
Insider Trading Arr Line Items
Material Terms of Trading Arrangement [Text Block]		Item 5. Other Information Trading Arrangements During the three-month period ended June 30, 2024, none of our directors or officers (as defined in Rule 16a-1(f) under the Exchange Act) adopted or terminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement” as such terms are defined under Item 408 of Regulation S-K.
Rule 10b5-1 Arrangement Adopted [Flag]	false
Non-Rule 10b5-1 Arrangement Adopted [Flag]	false
Rule 10b5-1 Arrangement Terminated [Flag]	false
Non-Rule 10b5-1 Arrangement Terminated [Flag]	false

Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2024

Accounting Policies [Abstract]

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation

Consolidation, Policy [Policy Text Block]

Principles of Consolidation

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

Share-Based Payment Arrangement [Policy Text Block]

Stock-Based Compensation

The Company's stock-based compensation programs include stock options and an employee stock purchase program.

See Note 6 for a detailed discussion of the Company’s stock plans and stock-based compensation expense.

Standard Product Warranty, Policy [Policy Text Block]

Product Warranty

Warranty accrual activity consisted of the following for the three-month and six-month periods ended June 30, 2024 and 2023 (in thousands):

	*Three Months Ended June 30,*					*Six Months Ended June 30,*
	*2024*		*2023*			*2024*		*2023*
Beginning balance	$	—	$	50		$	—	$	50
Add: Accruals for warranties issued during the period		—		—			—		—
Less: Adjustment for inventory at cost and excessive and obsolete inventory		—		(50	)		—		(50	)
Ending balance	$	—	$	—		$	—	$	—

Earnings Per Share, Policy [Policy Text Block]

Net Loss per Share

Basic and diluted net loss per common share is the same for all periods presented because all warrants, stock options and restricted stock units outstanding are anti-dilutive.

	*Six Months Ended June 30,*
	*2024*		*2023*
Common stock options		11,596,762		6,888,015
Total		11,596,762		6,888,015

New Accounting Pronouncements, Policy [Policy Text Block]

Recent Accounting Pronouncements Not Yet Adopted

Disclosure of accounting policy for award under share-based payment arrangement. Includes, but is not limited to, methodology and assumption used in measuring cost.

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Note 9 - Segment Reporting

6 Months Ended

Jun. 30, 2024

Segment Reporting Disclosure [Text Block]

9. Segment Reporting

The Company operates and manages the business as one reportable and operating segment. The Company’s Chief Executive Officer acts as the chief operating decision maker (“CODM”) of the Company. The CODM reviews the results of the Company on a consolidated basis. All of the Company’s long-lived assets are based in the United States.

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities:
Net loss	$ (21,520)	$ (19,711)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	264	271
Amortization of intangible assets	333	333
Stock-based compensation	3,811	2,039
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(82)	(309)
Other receivables	3	106
Right-of-use assets	438	392
Accounts payable	(286)	212
Accrued expenses	(635)	239
Lease liabilities	(501)	(421)
Accrued interest on related party note payable	0	1,077
Net cash used in operating activities	(18,175)	(15,772)
Cash flows from investing activities:
Purchases of property and equipment	(34)	(55)
Net cash used in investing activities	(34)	(55)
Cash flows from financing activities:
Proceeds from issuance of common stock under employee stock purchase plan	296	292
Proceeds from exercises of warrants	0	14,835
Proceeds from exercises of stock options	22	58
Issuance cost in relation to related party note extinguishment	0	(5)
Payments made on related party note	0	(1,745)
Issuance costs in relation to future rights offering	(278)	0
Net cash provided by financing activities	40	13,435
Net decrease in cash and cash equivalents	(18,169)	(2,392)
Cash and cash equivalents at beginning of period	44,365	61,139
Cash and cash equivalents at end of period	26,196	58,747
Equipment purchases included in accounts payable and accrued expenses	16	10
Rights offering deemed pro-rata distribution to shareholders	47,700	0
Principal and accrued interest of related party note settled via issuance of common stock	0	65,248
Issuance costs in accounts payable and accrued expenses	$ 71	$ (8)

Note 6 - Stockholders' Equity and Stock-based Compensation - ESPP Assumptions (Details) - The 2017 Employee Stock Purchase Plan [Member]	3 Months Ended		6 Months Ended		15 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024
Expected volatility	98.00%	83.00%	98.00%	83.00%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member]
Expected term in years (Year)	6 months	6 months	6 months	6 months
Risk-free interest rate	4.90%	5.10%	4.90%	5.10%
Maximum [Member]
Expected term in years (Year)	1 year		1 year	1 year	1 year
Risk-free interest rate	5.30%		5.30%	5.20%	5.20%

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Performance Option Activity (Details) - Performance Options [Member]	6 Months Ended	12 Months Ended
	Jun. 30, 2024 $ / shares shares	Dec. 31, 2023 $ / shares shares
Options balances, number of shares (in shares) \| shares	1,224,130
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 5.51
Options balances, weighted average remaining life (Year)	8 years 1 month 6 days	8 years 6 months 10 days
Options granted, number of shares (in shares) \| shares	39,000
Options granted, weighted average exercise price (in dollars per share) \| $ / shares	$ 8.44
Options exercised, number of shares (in shares) \| shares	(4,000)
Options exercised, weighted average exercise price (in dollars per share) \| $ / shares	$ 2.92
Options canceled, number of shares (in shares) \| shares	(3,000)
Options canceled, weighted average exercise price (in dollars per share) \| $ / shares	$ 2.92
Options expired, number of shares (in shares) \| shares	(1,000)
Options expired, weighted average exercise price (in dollars per share) \| $ / shares	$ 2.92
Options balances, number of shares (in shares) \| shares	1,255,130	1,224,130
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 5.62	$ 5.51
Options exercisable, number of shares (in shares) \| shares	438,628
Options exercisable, weighted average exercise price (in dollars per share) \| $ / shares	$ 7.63
Options exercisable, weighted average remaining life (Year)	7 years 3 months 3 days

Note 7 - Research Grants and Agreements

6 Months Ended

Jun. 30, 2024

Research, Development, and Computer Software Disclosure [Text Block]

7. Research Grants and Agreements

Sponsored Research Agreement

The Company may sponsor research activities (“SRAs”) performed by ODURF. ODURF is compensated by the Company for its conduct of each study in accordance with the budget and payment terms set forth in the applicable task order. Task orders are typically performed over a 12-month period and funded through monthly payments to ODURF. Payments will be made upon ODURF certifying, to the Company’s reasonable satisfaction, that ODURF has met its obligations pursuant to the specified task order and statement of work. The principal investigator may transfer funds with the budget as needed without the Company’s approval so long as the obligations of ODURF under the task order and statement of work remain unchanged and unimpaired. During the three-month and six-month periods ended June 30, 2024 and 2023, the Company did not incur any costs relating to any SRAs. As of June 30, 2024, the Company does not have any active SRAs with ODURF.

Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 26,196	$ 44,365
Prepaid expenses and other current assets	1,043	963
Total current assets	27,239	45,328
Property and equipment, net	1,313	1,528
Intangible assets, net	1,553	1,886
Goodwill	2,791	2,791
Right-of-use assets	6,818	7,256
Other assets	714	365
Total assets	40,428	59,154
Current liabilities:
Accounts payable	1,637	1,836
Accrued expenses	3,179	3,814
Lease liability, current	1,146	1,058
Total current liabilities	5,962	6,708
Lease liability, less current portion	7,497	8,086
Total liabilities	13,459	14,794
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; authorized – 50,000 shares; no shares issued and outstanding	0	0
Common stock, $0.001 par value; authorized – 500,000 shares; issued and outstanding – 55,228 shares and 55,144 shares at June 30, 2024 and December 31, 2023 respectively	55	55
Additional paid-in capital	385,349	381,220
Accumulated other comprehensive income (loss)	0	0
Accumulated deficit	(358,435)	(336,915)
Total stockholders’ equity	26,969	44,360
Total liabilities and stockholders’ equity	$ 40,428	$ 59,154

Note 8 - Commitments and Contingencies

6 Months Ended

Jun. 30, 2024

Commitments and Contingencies Disclosure [Text Block]

8. Commitments and Contingencies

2022 Loan Agreement

On September 20, 2022, the Company and Robert W. Duggan, the Company's majority stockholder and Executive Chairman, entered into a Loan Agreement (“2022 Loan Agreement”) in connection with Mr. Duggan lending the principal sum of $65.0 million to the Company. The 2022 Loan Agreement bore interest at a rate per annum equal to 5.0%, payable quarterly commencing on January 1, 2023, with the principal sum payable on March 20, 2024. On March 17, 2023, the Company and Mr. Duggan amended certain terms of the 2022 Loan Agreement. There were no changes to the interest rate, but the principal sum repayment date was changed to September 30, 2024. During the year ended December 31, 2023, the Company made cash payments of $1.7 million for accrued interest on the loan, and recorded an additional $1.1 million of interest expense in relation to the 2022 Loan Agreement. On April 30, 2023, the Company entered into a Securities Purchase Agreement with Mr. Duggan, pursuant to which the Company agreed to issue and sell to Mr. Duggan 10,022,937 shares of the Company’s common stock, par value $0.001 per share, in a Private Placement, at a price per share of $6.51. These shares were paid for through the cancellation of the amounts then owed by the Company under the 2022 Loan Agreement, the principal sum of $65.0 million and all accrued and unpaid interest outstanding, which totaled approximately $0.2 million as of April 30, 2023. The parties completed the Private Placement on May 9, 2023 and, upon closing and satisfaction of the outstanding debt, the 2022 Loan Agreement terminated, without early termination fees or penalties being owed by the Company. No additional amounts are owed to Mr. Duggan under the 2022 Loan Agreement.

Operating Leases

In January 2017, the Company entered into a five-year lease (the “Existing Lease”) for approximately 15,700 square feet for its corporate headquarters located in Hayward, California. The lease commenced in July 2017.

In May 2019, the Company entered into Lease Amendment 1 (the “Lease Amendment”) in relation to the Existing Lease and added the lease of new premises of approximately 13,300 square feet and 21,300 square feet, (“Expansion Premises 1” and “Expansion Premises 2”, respectively). Additionally, the term of the Existing Lease was extended to October 2029 to be coterminous with Expansion Premises 1 and Expansion Premises 2.

The Company evaluated the lease amendment under the provisions of ASC 842. It concluded that the Lease Amendment would be accounted for as a single contract with the Existing Lease because the additional lease payments due to the Lease Amendment was not commensurate with the right-of-use asset granted to the Company. Though the Lease Amendment was accounted for as a single contract, the Existing Premises, Expansion Premises 1 (occupied in November 2019) and Expansion Premises 2 (occupied in May 2020) are accounted for as separate lease components. Accordingly, the Company measured and allocated consideration to each lease component as of the modification date.

Supplemental balance sheet information related to leases (in thousands):

	*June 30,*		*December 31,*
Assets:	*2024*		*2023*
Right-of-use assets	$	6,818	$	7,256

	*June 30,*		*December 31,*
Liabilities:	*2024*		*2023*
Current operating lease liabilities	$	1,146	$	1,058
Non-current operating lease liabilities		7,497		8,086
Total lease liabilities	$	8,643	$	9,144

Total cash paid for operating lease liabilities (in thousands):

	*Six Months Ended June 30,*
	*2024*		*2023*
Cash paid for operating lease liabilities	$	940	$	907

Maturities of operating lease liabilities were as follows (in thousands):

Year ending December 31:
2024 (remaining 6 months)	$	970
2025		1,977
2026		2,046
2027		2,117
Thereafter		4,074
Total lease payments		11,184
Less imputed interest		(2,541	)
Total lease liabilities	$	8,643

Weighted-average remaining lease term and discount rate, as of June 30, 2024, were as follows:

Weighted-average remaining lease term			5.34
Weighted-average discount rate			10	%

Rent expense, including common area maintenance charges, was approximately $0.6 million and $0.5 million for the three-month periods ended June 30, 2024 and 2023, respectively, and was approximately $1.2 million and $1.0 million for the six-month periods ended June 30, 2024 and 2023, respectively.

Legal Proceedings

From time to time, we may be involved in a variety of claims, lawsuits, investigations, and proceedings relating to securities laws, product liability, patent infringement, contract disputes, and other matters relating to various claims that arise in the normal course of our business, including the matter described below. The outcome of any legal proceedings is unpredictable but, regardless of outcome, they can have an adverse impact on us because of defense and settlement costs, diversion of management resources, negative publicity, reputational harm, and other factors. We maintain insurance that may provide coverage for such matters, including customary employment practices liability insurance.

In November 2022, the employment of our former Chief Financial Officer, Sandra Gardiner, terminated. Ms. Gardiner’s departure was not the result of any disagreement with the Company on any matter relating to its operations, accounting policies or practices, although the Company determined that she was not eligible to receive any severance benefits under the terms and conditions of her then existing employment agreement. In March 2023, Ms. Gardiner filed an arbitration demand with JAMS seeking severance benefits and other remedies, alleging breach of contract and unlawful termination in violation of public policy, among other things. We believe that Ms. Gardiner’s claims are without merit and we intend to vigorously defend ourselves against them. Because of the difficulty in predicting the outcome of any legal proceeding, particularly one that is in its early stages, the Company is not able to conclude that a liability is probable and cannot predict what the final outcome of Ms. Gardiner’s arbitration proceeding will likely be or provide a reasonable estimate for the range of ultimate possible loss, if any. However, at this time, we believe that the final resolution of this matter will not adversely affect our consolidated position, results of operations, or cash flows and that a liability is not probable at this time.

Note 11 - Restructuring Charges (Details Textual) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)
Income Statement [Abstract]
Costs and Expenses		$ 11,726	$ 10,227	$ 22,341	$ 19,789
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]	Costs and Expenses
Employee Severance [Member]
Restructuring and Related Cost, Number of Positions Eliminated	7
Restructuring Charges	$ 100

Note 12 - Subsequent Events (Details Textual) - USD ($) $ / shares in Units, $ in Millions	Jul. 03, 2024	Jun. 09, 2022	Jun. 30, 2024	Dec. 31, 2023
Common Stock, Par or Stated Value Per Share (in dollars per share)			$ 0.001	$ 0.001
Rights Offering Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)		1
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				7,317,072
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 2.05		$ 2.05
Subsequent Event [Member] \| Rights Offering Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	6,000,000
Class of Warrant or Right, Proceeds Upon Exercise	$ 66
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 11
Class of Warrans or Right, Exercise Price, Percentage of Subscription Price for Units	110.00%
Warrants and Rights Outstanding, Term (Year)	5 years
Subsequent Event [Member] \| Rights Offering Warrants [Member] \| Vesting of First Half [Member]
Class of Warrant or Right, Vesting, Stock Price Trigger (in dollars per share)	$ 16.5
Subsequent Event [Member] \| Rights Offering Warrants [Member] \| Vesting of Second Half [Member]
Class of Warrant or Right, Vesting, Stock Price Trigger (in dollars per share)	$ 22
Rights Offering [Member]
Shares Issued, Price Per Share (in dollars per share)		$ 2.05
Number of Shares Per Unit Issued (in shares)		1
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001
Stock Issued During Period, Shares, New Issues (in shares)		7,317,072
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		7,317,072
Proceeds from Issuance of Common Stock		$ 15
Rights Offering [Member] \| Subsequent Event [Member]
Equity Offering, Units, Maximum Amount Authorized (in shares)	6,000,000
Shares Issued, Price Per Share (in dollars per share)	$ 10
Number of Shares Per Unit Issued (in shares)	1
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.001
Number of Warrants in Each Unit (in shares)	2
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)	0.5
Stock Issued During Period, Shares, New Issues (in shares)	5,999,999
Proceeds from Issuance of Common Stock	$ 60
Rights Offering [Member] \| Subsequent Event [Member] \| Executive Chairman [Member]
Stock Issued During Period, Shares, New Issues (in shares)	5,000,000
Investment Owned, Percent of Net Assets	73.00%

Note 5 - Goodwill

6 Months Ended

Jun. 30, 2024

Goodwill Disclosure [Text Block]

5. Goodwill

In 2014, the Company acquired three companies (the “Acquisitions”) for aggregate consideration of $5.5 million. In accordance with ASC Topic 805, Business Combinations, the Company recorded goodwill of $2.8 million in connection with the Acquisitions as the consideration paid exceeded the fair value of the net tangible assets and the intangible assets acquired.

In accordance with ASC Topic 350, Intangibles-Goodwill and Other (as amended by Accounting Standards Update 2017-04), the Company reviews goodwill for impairment at least annually or whenever any events or circumstances indicate that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. As of June 30, 2024, there were no indicators of impairment and it was determined that no impairment of goodwill existed.

Note 10 - Related Party Transactions

6 Months Ended

Jun. 30, 2024

10. Related Party Transactions

In May 2022, the Company determined not to renew its annual director and officer liability insurance policy due to disproportionately high premiums quoted by insurance companies. Instead, on May 31, 2022, the Company and Robert W. Duggan, majority stockholder and Executive Chairman, entered into a letter agreement (the “Letter Agreement”) pursuant to which Mr. Duggan agreed with the Company to personally provide indemnity coverage for a one-year period, and he agreed to deposit cash and/or marketable securities into a third-party escrow, as security for these obligations, if requested by the Company. On May 31, 2023, the last day of the one-year period, the Company paid Mr. Duggan a fee of $1.0 million in consideration of the obligations set forth in the Letter Agreement. As of June 30, 2024, there were no additional amounts owed to Mr. Duggan under the Letter Agreement.

On September 20, 2022, the Company and Robert W. Duggan, the Company's majority stockholder and Executive Chairman, entered into the 2022 Loan Agreement in connection with Mr. Duggan lending the principal sum of $65.0 million to the Company. On April 30, 2023, the Company entered into a Securities Purchase Agreement with Mr. Duggan, pursuant to which the Company agreed to issue and sell to Mr. Duggan 10,022,937 shares of the Company’s common stock, par value $0.001 per share, in a Private Placement, at a price per share of $6.51. These shares were paid for through the cancellation of the amounts then owed by the Company under the 2022 Loan Agreement, the principal sum of $65.0 million and all accrued and unpaid interest outstanding, which totaled approximately $0.2 million as of April 30, 2023. Upon closing of the Private Placement and satisfaction of the outstanding debt, the 2022 Loan Agreement terminated, without early termination fees or penalties being owed by the Company. No additional amounts are owed to Mr. Duggan under the 2022 Loan Agreement. See Note 8 for further details.

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

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