Cardiff Oncology (CRDF) 10-K 24 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 17, 2022	Jun. 30, 2021
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-35558
Entity Registrant Name	CARDIFF ONCOLOGY, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-2004382
Entity Address, State or Province	CA
Entity Address, City or Town	San Diego
Entity Address, Address Line One	11055 Flintkote Avenue
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	952-7570
Title of 12(b) Security	Common Stock, $0.0001 par value
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 258,944,643
Entity Common Stock, Shares Outstanding (shares)		43,306,061
Entity Central Index Key	0001213037
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Firm ID	243
Auditor Name	BDO USA, LLP
Auditor Location	San Diego, California

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 11,943	$ 130,981
Short-term investments	128,878	0
Accounts receivable and unbilled receivable	535	320
Prepaid expenses and other current assets	4,771	2,055
Total current assets	146,127	133,356
Property and equipment, net	382	624
Operating lease right-of-use assets	2,796	343
Other assets	239	404
Total Assets	149,544	134,727
Current liabilities:
Accounts payable	1,439	1,366
Accrued liabilities	4,527	3,851
Operating lease liabilities	551	860
Other current liabilities	42	42
Total current liabilities	6,559	6,119
Derivative financial instruments—warrants	0	285
Operating lease liabilities, net of current portion	2,568	9
Other liabilities	0	156
Total liabilities	9,127	6,569
Commitments and contingencies
Stockholders’ equity
Preferred stock, $0.001 par value, 20,000 shares authorized; (Note 5)	1	1
Common stock, $0.0001 par value, 150,000 shares authorized; 41,964 and 36,781 shares issued and outstanding at December 31, 2021 and December 31, 2020, respectively	4	4
Additional paid-in capital	400,503	361,819
Service receivable	(139)	(2,171)
Accumulated other comprehensive loss	(142)	0
Accumulated deficit	(259,810)	(231,495)
Total stockholders’ equity	140,417	128,158
Total Liabilities and Stockholders’ Equity	$ 149,544	$ 134,727

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	20,000	20,000
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	150,000	150,000
Common stock, shares issued (in shares)	41,964	36,781
Common stock, shares outstanding (in shares)	41,964	36,781

Statements of Operations

Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Royalty revenues	$ 359	$ 366
Costs and expenses:
Research and development	17,376	11,235
Selling, general and administrative	11,838	8,217
Total operating expenses	29,214	19,452
Loss from operations	(28,855)	(19,086)
Other income (expense), net:
Interest income	264	90
Interest expense	0	(2)
Other gain (loss), net	15	(28)
Gain (loss) from changes in fair value of derivative financial instruments—warrants	285	(281)
Total other income (expense), net	564	(221)
Net loss	(28,291)	(19,307)
Preferred stock dividend payable on Series A Convertible Preferred Stock	(24)	(24)
Net loss attributable to common stockholders	$ (28,315)	$ (22,598)
Net loss per common share - basic (in dollars per share)	$ (0.73)	$ (1.08)
Net loss per common share - diluted (in dollars per share)	$ (0.73)	$ (1.08)
Weighted-average shares outstanding - basic (in shares)	39,030	20,875
Weighted-average shares outstanding - diluted (in shares)	39,030	20,875
Series D Convertible Preferred Stock
Other income (expense), net:
Deemed dividend recognized on beneficial conversion features of Convertible Preferred Stock issuance	$ 0	$ (602)
Series E Convertible Preferred Stock
Other income (expense), net:
Deemed dividend recognized on beneficial conversion features of Convertible Preferred Stock issuance	$ 0	$ (2,665)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Net loss	$ (28,291)	$ (19,307)
Unrealized loss on securities available-for-sale	(142)	0
Comprehensive loss	(28,433)	(19,307)
Preferred stock dividend payable on Series A Convertible Preferred Stock	(24)	(24)
Comprehensive loss attributable to common stockholders	(28,457)	(22,598)
Series D Convertible Preferred Stock
Deemed dividend recognized on beneficial conversion features of Convertible Preferred Stock issuance	0	(602)
Series E Convertible Preferred Stock
Deemed dividend recognized on beneficial conversion features of Convertible Preferred Stock issuance	$ 0	$ (2,665)

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total	Series D Convertible Preferred Stock	Series E Convertible Preferred Stock	Preferred Stock	Preferred StockSeries D Convertible Preferred Stock	Preferred StockSeries E Convertible Preferred Stock	Common Stock	Common StockSeries D Convertible Preferred Stock	Common StockSeries E Convertible Preferred Stock	Additional Paid-In Capital	Additional Paid-In CapitalSeries D Convertible Preferred Stock	Additional Paid-In CapitalSeries E Convertible Preferred Stock	Service Receivable	Accumulated other comprehensive loss	Accumulated Deficit	Accumulated DeficitSeries D Convertible Preferred Stock	Accumulated DeficitSeries E Convertible Preferred Stock
Balance (in shares) at Dec. 31, 2019					61			8,594
Balance at Dec. 31, 2019		$ 7,312			$ 0			$ 8			$ 217,173			$ (972)	$ 0	$ (208,897)
Increase (Decrease) in Stockholders' Equity
Sale of stock, shares issued (in shares)	[1]				866			12,964
Net proceeds	[1]	112,300			$ 1			$ 1			112,298
Issuance of common stock, preferred stock and warrants for clinical trial funding commitment, net of expenses and discount (in shares)					155			603
Issuance of common stock, preferred stock and warrants for clinical trial funding commitment, net of expenses and discount		(8)									2,292			(2,300)
Stock-based compensation		1,765									1,765
Issuance of common stock upon exercise of warrants (in shares)								12,138
Issuance of common stock upon exercise of warrants		24,871						$ 1			24,870
Issuance of common stock upon vesting of restricted stock awards (in shares)								11
Deemed dividend recognized on beneficial conversion features of Series C Convertible Preferred Stock issuance			$ 0	$ 0								$ 602	$ 2,665				$ (602)	$ (2,665)
Issuance of common stock upon conversion of Convertible Preferred Stock (in shares)						(155)	(211)		1,547	864
Preferred stock dividend payable on Series A Convertible Preferred Stock		(24)														(24)
Release of clinical trial funding commitment		1,101												1,101
Common Stock par value adjustment		0						$ (6)			6
Issuance of common stock upon exercise of stock options (in shares)								60
Issuance of common stock upon exercise of stock options		148									148
Net loss		(19,307)														(19,307)
Unrealized loss on securities available-for-sale		0
Balance (in shares) at Dec. 31, 2020					716			36,781
Balance at Dec. 31, 2020		128,158			$ 1			$ 4			361,819			(2,171)	0	(231,495)
Increase (Decrease) in Stockholders' Equity
Sale of stock, shares issued (in shares)	[2]							4,412
Net proceeds	[2]	34,187									34,187
Stock-based compensation		3,234									3,234
Issuance of common stock upon exercise of warrants (in shares)								771
Issuance of common stock upon exercise of warrants		1,263									1,263
Preferred stock dividend payable on Series A Convertible Preferred Stock		(24)														(24)
Release of clinical trial funding commitment		2,032												2,032
Net loss		(28,291)														(28,291)
Unrealized loss on securities available-for-sale		(142)													(142)
Balance (in shares) at Dec. 31, 2021					716			41,964
Balance at Dec. 31, 2021		$ 140,417			$ 1			$ 4			$ 400,503			$ (139)	$ (142)	$ (259,810)
[1]	Net of expenses of $7.5 million, and fair value of warrants issued as a transaction advisory fee as of the date of issuance of $0.4 million.
[2]	Net of expenses of $0.8 million.

Statement of Shareholders' Equi

Statement of Shareholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2020USD ($)
Statement of Stockholders' Equity [Abstract]
Cost of Issuance of Common Stock, Preferred Stock and Warrants for Clinical Trial Funding Commitment	$ 7,500,000
Fair value	$ 400,000

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating activities
Net loss	$ (28,291)	$ (19,307)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss on disposal of assets	1	0
Impairment loss	0	34
Depreciation	451	466
Stock-based compensation expense	3,234	1,765
Amortization of premiums on short-term investments	1,607	0
Change in fair value of derivative financial instruments—warrants	(285)	281
Release of clinical trial funding commitment	2,032	1,100
Changes in operating assets and liabilities:
Other assets	166	(246)
Accounts receivable and unbilled receivable	(215)	(117)
Prepaid expenses and other current assets	(2,099)	(1,100)
Operating lease right-of-use assets	607	320
Accounts payable and accrued expenses	719	1,276
Operating lease liabilities	(811)	(857)
Other liabilities	(156)	70
Net cash used in operating activities	(23,040)	(16,315)
Investing activities
Capital expenditures	(205)	(211)
Maturities of short-term investments	28,391	0
Purchases of short-term investments	(174,385)	0
Sales of short-term investments	14,751	0
Net cash used in investing activities	(131,448)	(211)
Financing activities
Proceeds from sale of common stock, preferred stock and warrants, net of expenses of $813 and $7,507 respectively	34,187	112,300
Costs related to the clinical trial funding commitment	0	(8)
Proceeds from exercise of warrants	1,263	24,872
Proceeds from exercise of options	0	148
Borrowings under note payable	0	305
Repayments of note payable	0	(305)
Net cash provided by financing activities	35,450	137,312
Net change in cash and cash equivalents	(119,038)	120,786
Cash and cash equivalents—Beginning of period	130,981	10,195
Cash and cash equivalents—End of period	11,943	130,981
Supplementary disclosure of cash flow activity:
Cash paid for taxes	1	1
Acquisition of property and equipment included in accounts payable and accrued liabilities	6	0
Supplemental disclosure of non-cash investing and financing activities:
Preferred stock dividend payable on Series A Convertible Preferred Stock	24	24
Series D Convertible Preferred Stock
Supplemental disclosure of non-cash investing and financing activities:
Deemed dividend recognized on beneficial conversion features of convertible preferred stock	0	602
Common stock, Series D Convertible Preferred Stock and warrants issued in connection with clinical trial funding commitment, net of discount of $0 and $488, respectively	0	2,300
Series E Convertible Preferred Stock
Supplemental disclosure of non-cash investing and financing activities:
Deemed dividend recognized on beneficial conversion features of convertible preferred stock	$ 0	$ 2,665

Statements of Cash Flows (Paren

Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Payments of stock issuance costs	$ 800
Common Stock And Warrants
Payments of stock issuance costs	813	$ 7,507
Series D Convertible Preferred Stock
Discount of issuance of common stock, preferred stock and warrants for clinical trial funding commitment	$ 0	$ 488

Business Overview and Liquidity

Business Overview and Liquidity	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business Overview and Liquidity	Business Overview and Liquidity Business Organization and Overview Cardiff Oncology, Inc. (“Cardiff Oncology” or the “Company”) headquartered in San Diego, California, is a clinical-stage oncology company with the mission of developing new precision medicine treatment options for cancer patients in indications with the greatest unmet medical need, including KRAS-mutated metastatic colorectal cancer, metastatic pancreatic cancer and metastatic castration-resistant prostate cancer. The Company's common stock is listed on the Nasdaq Capital Market under the ticker symbol "CRDF". Liquidity The Company has incurred net losses since its inception and has negative operating cash flows. As of December 31, 2021, the Company had $140.8 million in cash, cash equivalents and short-term investments and believes it has sufficient cash to meet its funding requirements for at least the next 12 months following the issuance date of these financial statements. For the foreseeable future, the Company expects to continue to incur losses and require additional capital to further advance its clinical trial programs and support its other operations. The Company cannot be certain that additional funding will be available on acceptable terms, or at all. To the extent that the Company can raise additional funds by issuing equity securities, the Company’s stockholders may experience additional dilution. The economic effects of COVID-19 could also have an adverse effect on the Company's ability to raise additional capital. See Note 13 to the financial statements for further information.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies The accompanying financial statements of Cardiff Oncology have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations as, and manages its business in, one operating segment. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make significant estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The most significant estimate involves accrued clinical trial expenses. Accrued Clinical Trial Expenses The Company expenses research and development expenditures as incurred, which include costs related to clinical trial activities. The Company accrues costs for clinical trial activities based upon estimates of the services received and related expenses incurred that have yet to be invoiced by the Clinical Research Organizations ("CROs"), investigators, professional service providers, and other vendors providing clinical trial services (collectively, the “service providers”). As of December 31, 2021 the Company’s clinical trial accrual balance of $1.6 million is included in accrued liabilities. The Company’s related 2021 clinical trial expenses are included in research and development expense of $17.4 million. Certain clinical trial expenses are released from service receivables classified within equity (see Note 5) as clinical trial services are performed. Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents consist of cash in readily available checking and money market accounts. Investment Securities All investments have been classified as “available-for-sale” and are carried at fair value as determined based upon quoted market prices or pricing models for similar securities at period end. Investments with contractual maturities less than 12 months at the balance sheet date are considered short-term investments. Investments with contractual maturities beyond one year are also classified as short-term due to the Company’s ability to liquidate the investment for use in operations within the next 12 months. Realized gains and losses on investment securities are included in earnings and are derived using the specific identification method for determining the cost of securities sold. The Company has not realized any significant gains or losses on sales of available-for-sale investment securities during any of the periods presented. As all the Company’s investment holdings are in the form of debt securities or certificates of deposit, unrealized gains and losses that are determined to be temporary in nature are reported as a component of accumulated other comprehensive loss. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. Interest income is recognized when earned and is included in investment income, as are the amortization of purchase premiums and accretion of purchase discounts on investment securities. Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains deposit accounts at financial institutions that are in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash due to the financial position of the depository institution in which those deposits are held. The Company limits its exposure to credit loss by generally placing its cash in high credit quality financial institutions and investment in non FDIC insured money market funds denominated and payable in U.S. dollars. Revenues The Company recognizes revenue when control of its products and services are transferred to its customers in an amount that reflects the consideration it expects to receive from its customers in exchange for those products and services. This process involves identifying the contract with a customer, determining the performance obligations in the contract, determining the contract price, allocating the contract price to the distinct performance obligations in the contract, and recognizing revenue when the performance obligations have been satisfied. A performance obligation is considered distinct from other obligations in a contract when it provides a benefit to the customer either on its own or together with other resources that are readily available to the customer and is separately identified in the contract. The Company considers a performance obligation satisfied once it has transferred control of goods or service to the customer, meaning the customer has the ability to use and obtain the benefit of goods or service. The Company recognizes revenue for satisfied performance obligations only when it determines there are no uncertainties regarding payment terms or transfer of control. For sales-based royalties, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Royalty and License Revenues The Company licenses and sublicenses its patent rights to healthcare companies, medical laboratories and biotechnology partners. These patents are from the Company's legacy portfolio and unrelated to onvasertib. Agreements may involve multiple elements such as license fees, minimum royalties, usage-based royalties and milestone payments. Revenue is recognized when the criteria described above have been met as well as the following: • Up-front nonrefundable license fees pursuant to agreements under which the Company has no continuing performance obligations are recognized as revenues on the effective date of the agreement and when collection is probable. • Minimum royalties are recognized as earned, and royalties are earned based on the licensee’s use. The Company estimates and records licensee’s sales based on historical usage rate and collectability. • For sales-based royalties, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Payment terms and conditions vary by contracts, although terms generally include a requirement of payment within 30 to 45 days after invoice. Royalties are generally due quarterly or annually. Derivative Financial Instruments—Warrants The Company has issued common stock warrants in connection with the execution of certain equity financings. Such warrants are classified as derivative liabilities and are recorded at their fair market value as of each reporting period as they do not meet the criteria for equity classification. Changes in fair value of derivative liabilities are recorded in the statement of operations under the caption “Change in fair value of derivative instruments — warrants.” The fair value of warrants is determined using the Black-Scholes option-pricing model using assumptions regarding the historical volatility of Cardiff Oncology’s common stock price, the remaining life of the warrants, and the risk-free interest rates at each period end. The Company thus uses model-derived valuations where inputs are observable in active markets to determine the fair value. The use of the Black-Scholes model classifies such warrants as Level 3 (See " Fair Value of Financial Instruments" below). At December 31, 2021 and 2020, the fair value of these warrants was $0 and $285,000, respectively, and was recorded as a liability under the caption “derivative financial instruments — warrants” on the balance sheets. These warrants expire in the first quarter of 2023. Stock-Based Compensation Stock-based compensation expense is measured at the grant date based on the estimated fair value of the award and is recognized straight-line over the requisite service period of the individual grants, which typically equals the vesting period. Fair Value of Financial Instruments Financial instruments consist of cash equivalents, accounts receivable, accounts payable and derivative liabilities. The Company applies ASC 820 for financial assets and liabilities that are required to be measured at fair value and non-financial assets and liabilities that are not required to be measured at fair value on a recurring basis. These financial instruments are stated at their respective historical carrying amounts, which approximate fair value due to their short-term nature as they reflect current market interest rates. The authoritative guidance establishes a fair value hierarchy that is based on the extent and level of judgment used to estimate the fair value of assets and liabilities. In general, the authoritative guidance requires us to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. An asset or liability’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the measurement of its fair value. The three levels of input defined by the authoritative guidance are as follows: The Company measures certain assets and liabilities at fair value on a recurring basis using the three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. The three tiers include: • Level 1 — Quoted prices for identical instruments in active markets. • Level 2 — Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations where inputs are observable or where significant value drivers are observable. • Level 3 — Instruments where significant value drivers are unobservable to third parties. Long-Lived Assets Long-lived assets consist of property, equipment and lease right-of-use assets. The Company records property and equipment at cost. Depreciation on property and equipment is calculated using the straight-line method over the estimated useful life of the asset. Depreciation of leasehold improvements is computed based on the shorter of the life of the asset or the term of the lease. The estimated useful lives of the major classes of property and equipment are as follows: Estimated Useful Lives Furniture and office equipment 3 to 5 years Leasehold improvements 5 to 6 years Laboratory equipment 5 years Impairment losses on long-lived assets used in operations are recorded when indicators of impairment are present and the undiscounted cash flows estimated to be generated by those assets are less than the assets carrying amount. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the estimated fair value of the assets. Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease Right-of-Use (“ROU”) assets, current operating lease liabilities and non-current operating lease liabilities in the Company’s balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. None of the Company’s operating leases provide an implicit rate, therefore the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The incremental borrowing rate is the rate of interest that the Company would expect to pay to borrow on a collateralized and fully amortizing basis over a similar term an amount equal to the lease payments in a similar economic environment. The operating lease ROU asset also includes any lease payments made less lease incentives received. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. Our facilities lease agreement contains lease and non-lease components, such as common area maintenance. We have elected to account for these lease and non-lease components of this agreement as a single lease component. Leases with an initial term of 12 months or less are not recorded on the Company's balance sheets. These short-term leases are expensed on a straight-line basis over the lease term. Income Taxes Income taxes are determined using the asset and liability approach of accounting for income taxes. Under this approach, deferred taxes represent the future tax consequences expected to occur when the reported amounts of assets and liabilities are recovered or paid. Deferred taxes result from differences between the financial statement and tax bases of Cardiff Oncology’s assets and liabilities and are adjusted for changes in tax rates and tax laws when changes are enacted. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized. The assessment of whether or not a valuation allowance is required often requires significant judgment. Contingencies In the normal course of business, Cardiff Oncology is subject to loss contingencies, such as legal proceedings and claims arising out of its business, that cover a wide range of matters, including, among others, government investigations, stockholder lawsuits, product and environmental liability, and tax matters. In accordance with FASB ASC Topic 450, Contingencies , Cardiff Oncology records such loss contingencies when it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. Cardiff Oncology, in accordance with this guidance, does not recognize gain contingencies until realized. Research and Development Research and development expenses include expenditures in connection with an in-house research and development laboratory, salaries and staff costs, clinical trials, purchased in-process research and development and regulatory and scientific consulting fees, as well as contract research and insurance. Also, patent filing and patent maintenance expenses are considered legal in nature and therefore classified as general and administrative expense, if any. Non-refundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. As the related goods are delivered or the services are performed, or when the goods or services are no longer expected to be provided, the deferred amounts are recognized as an expense. Net Loss Per Share Basic and diluted net loss per common share is determined by dividing net loss applicable to common stockholders by the weighted-average common shares outstanding during the period. Preferred dividends and deemed dividends recognized in connection with certain preferred share issuances are included in net loss attributable to common stockholders in the computation of basic and diluted earnings per share. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as inclusion of the potentially dilutive securities would be antidilutive. Shares used in calculating diluted net loss per common share exclude as anti-dilutive the following share equivalents: December 31, 2021 2020 Options to purchase Common Stock 3,771,984 1,860,507 Warrants to purchase Common Stock 4,490,159 5,260,992 Restricted Stock Units — 491 Series A Convertible Preferred Stock 877 877 Series E Convertible Preferred Stock 2,684,607 2,684,607 10,947,627 9,807,474 Recent Accounting Pronouncement Not Yet Adopted In August 2020, the FASB issued ASU No. 2020-06 ("ASU 2020-06"), Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). ASU 2020-06 eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, ASU 2020-06 modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2021 (or December 15, 2023 for companies who meet the SEC definition of Smaller Reporting Companies), and interim periods within those fiscal years. The amendment is to be adopted through either a fully retrospective or modified retrospective method of transition. Early adoption is permitted. The Company is currently evaluating the impact of this standard on its financial statements and related disclosures. In May 2021, the FASB issued ASU No. 2021-04 ("ASU 2021-04), Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation—Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options (a consensus of the FASB Emerging Issues Task Force). The amendments in this update are effective for all entities for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. The Company will adopt this standard on January 1, 2022 and does not expect that the adoption of this standard will have a material impact on its financial statements and related disclosures.

Supplementary Balance Sheet Inf

Supplementary Balance Sheet Information	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplementary Balance Sheet Information	Supplementary Balance Sheet Information Short-term investments available-for-sale securities consist of the following: As of December 31, 2021 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Maturity less than 1 year: Certificate of deposit $ 1,260 $ — $ — $ 1,260 Corporate debt securities 58,822 2 (38) 58,786 Commercial paper 14,453 4 (3) 14,454 Non U.S. government 728 — — 728 U.S. treasury securities 20,380 — (24) 20,356 Total maturity less than 1 year 95,643 6 (65) 95,584 Maturity 1 to 2 years: Corporate debt securities 29,676 1 (73) 29,604 U.S. treasury securities 3,701 — (11) 3,690 Total maturity 1 to 2 years 33,377 1 (84) 33,294 Total short-term investments $ 129,020 $ 7 $ (149) $ 128,878 For the year ending December 31, 2021 the realized loss on the sale of short-term investments was $0. The Company did not have short-term investments during the year ending December 31, 2020. None of the Company’s short-term investments available for sale were in a material unrealized loss position at December 31, 2021. The Company reviewed its investment holdings as of December 31, 2021 and determined that its unrealized losses were not considered to be other-than-temporary based upon (i) the financial strength of the issuing institution and (ii) the fact that no securities have been in an unrealized loss position for twelve months or more. As such, the Company has not recognized any impairment in its financial statements related to its available-for-sale investment securities. Property and Equipment Fixed assets consist of furniture and office equipment, leasehold improvements and laboratory equipment. Depreciation expense for property and equipment for the years ended December 31, 2021 and 2020 was $0.5 million and $0.5 million, respectively. Property and equipment consisted of the following: As of December 31, (in thousands) 2021 2020 Furniture and office equipment $ 955 $ 798 Leasehold improvements 1,962 1,962 Laboratory equipment 906 868 3,823 3,628 Less—accumulated depreciation (3,441) (3,004) Property and equipment, net $ 382 $ 624 Accrued Liabilities Accrued liabilities consisted of the following: As of December 31, (in thousands) 2021 2020 Accrued compensation $ 1,435 $ 1,523 Preferred stock dividend 414 390 Clinical trials 1,639 1,557 Research agreements and services 726 67 Director fees 141 93 Professional fees and outside services 63 38 Patent, license and other fees 43 117 Other accrued liabilities 66 66 Total accrued liabilities $ 4,527 $ 3,851

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	Leases As a lessee, the Company’s current leases include its master facility lease and immaterial equipment leases, all of which are considered operating leases. The Company (as a sublessor) also subleases portions of its facility to third parties under three separate subleases. All of these subleases have been determined to be operating leases and are accounted for separately from the head lease. Master Facility Lease The Company currently occupies 9,500 square feet of office and lab space in San Diego. During July 2021, the Company entered into an amended lease agreement to increase its occupied space to 12,300 square feet which commences on January 1, 2022 and expires on February 28, 2027. Under the current master facility lease, which expired on December 31, 2021, the Company leases 26,100 square feet of office and lab space. This includes 16,600 square feet of space that is subleased to third parties, all of which expired on December 31, 2021. The minimum monthly rent under the amended lease is $55,000 with an annual rent escalation of 3% per year beginning on January 1, 2022. Through December 31, 2021 rent payments were approximately $80,000 per month. Facility Subleases As a result of corporate restructurings in previous years, the Company vacated a portion of its facility and has subleased the space to third parties under three separate sublease agreements, which all expired on December 31, 2021. Prior to the expiration of the sublease agreements, the Company as a sublessor was leasing approximately 16,600 square feet of space to third parties. The components of lease expense were as follows: (in thousands) Twelve Months Ended December 31, 2021 Twelve Months Ended December 31, 2020 Operating lease cost $ 745 $ 441 Operating sublease income (403) (291) Net operating lease cost $ 342 $ 150 Supplemental balance sheet information related to leases was as follows: (in thousands) As of December 31, 2021 As of December 31, 2020 Operating lease ROU assets $ 2,796 $ 343 Current operating lease liabilities $ 551 $ 860 Non-current operating lease liabilities 2,568 9 Total operating lease liabilities $ 3,119 $ 869 Weighted-average remaining lease term–operating leases 5.2 years 1.0 year Weighted-average discount rate–operating leases 7 % 6.5 % Supplemental cash flow and other information related to leases was as follows: (in thousands) Twelve Months Ended December 31, 2021 Twelve Months Ended December 31, 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 949 $ 944 ROU assets obtained in exchange for lease obligations: Operating leases $ 3,061 $ — Total remaining annual commitments under non-cancelable lease agreements for each of the years ended December 31 are as follows: (in thousands) Year Ending December 31, Operating Leases 2022 551 2023 737 2024 754 2025 775 2026 796 Thereafter 136 Total future minimum lease payments $ 3,749 Less imputed interest (630) Total $ 3,119
Leases	Leases As a lessee, the Company’s current leases include its master facility lease and immaterial equipment leases, all of which are considered operating leases. The Company (as a sublessor) also subleases portions of its facility to third parties under three separate subleases. All of these subleases have been determined to be operating leases and are accounted for separately from the head lease. Master Facility Lease The Company currently occupies 9,500 square feet of office and lab space in San Diego. During July 2021, the Company entered into an amended lease agreement to increase its occupied space to 12,300 square feet which commences on January 1, 2022 and expires on February 28, 2027. Under the current master facility lease, which expired on December 31, 2021, the Company leases 26,100 square feet of office and lab space. This includes 16,600 square feet of space that is subleased to third parties, all of which expired on December 31, 2021. The minimum monthly rent under the amended lease is $55,000 with an annual rent escalation of 3% per year beginning on January 1, 2022. Through December 31, 2021 rent payments were approximately $80,000 per month. Facility Subleases As a result of corporate restructurings in previous years, the Company vacated a portion of its facility and has subleased the space to third parties under three separate sublease agreements, which all expired on December 31, 2021. Prior to the expiration of the sublease agreements, the Company as a sublessor was leasing approximately 16,600 square feet of space to third parties. The components of lease expense were as follows: (in thousands) Twelve Months Ended December 31, 2021 Twelve Months Ended December 31, 2020 Operating lease cost $ 745 $ 441 Operating sublease income (403) (291) Net operating lease cost $ 342 $ 150 Supplemental balance sheet information related to leases was as follows: (in thousands) As of December 31, 2021 As of December 31, 2020 Operating lease ROU assets $ 2,796 $ 343 Current operating lease liabilities $ 551 $ 860 Non-current operating lease liabilities 2,568 9 Total operating lease liabilities $ 3,119 $ 869 Weighted-average remaining lease term–operating leases 5.2 years 1.0 year Weighted-average discount rate–operating leases 7 % 6.5 % Supplemental cash flow and other information related to leases was as follows: (in thousands) Twelve Months Ended December 31, 2021 Twelve Months Ended December 31, 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 949 $ 944 ROU assets obtained in exchange for lease obligations: Operating leases $ 3,061 $ — Total remaining annual commitments under non-cancelable lease agreements for each of the years ended December 31 are as follows: (in thousands) Year Ending December 31, Operating Leases 2022 551 2023 737 2024 754 2025 775 2026 796 Thereafter 136 Total future minimum lease payments $ 3,749 Less imputed interest (630) Total $ 3,119

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2021
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Warrants A summary of warrant activity and changes in warrants outstanding, including both liability and equity classifications, is presented below: Number of Weighted-Average Weighted-Average Remaining Contractual Term Balance outstanding, December 31, 2019 10,589,482 $ 4.08 3.7 years Granted 5,831,451 $ 1.70 Exercised (11,159,941) $ 2.31 Balance outstanding, December 31, 2020 5,260,992 $ 5.19 4.1 years Exercised (770,833) $ 1.64 Balance outstanding, December 31, 2021 4,490,159 $ 5.80 3.0 years The above table excludes pre-funded warrants with a nominal exercise price of $.01 per share: 1. 605,072 pre-funded warrants outstanding as of December 31, 2019; 2. 386,967 pre-funded warrants which were issued during the twelve months ending December 31, 2020; 3. All 992,039 pre-funded warrants were exercised in full during the twelve months ending December 31, 2020. Preferred Stock A summary of our Company's classes of preferred stock is presented below: Shares outstanding Class Par value Shares designated Liquidation preference As of December 31, 2021 As of December 31, 2020 Series A Convertible Preferred Stock $ 0.001 277,100 $ 606,000 60,600 60,600 Series B Convertible Preferred Stock $ 0.001 8,860 None — — Series C Convertible Preferred Stock $ 0.001 200,000 None — — Series D Convertible Preferred Stock $ 0.0001 154,670 None — — Series E Convertible Preferred Stock $ 0.001 865,824 None 655,044 655,044 Series A Convertible Preferred Stock The material terms of the Series A Convertible Preferred Stock consist of: 1) Dividends. Holders of the Company’s Series A Convertible Preferred Stock are entitled to receive cumulative dividends at the rate per share of 4% per annum, payable quarterly on March 31, June 30, September 30 and December 31, beginning with September 30, 2005. Dividends are payable, at the Company’s sole election, in cash or shares of common stock. As of December 31, 2021 and 2020, the Company had $414,000 and $390,000, respectively in accrued cumulative unpaid preferred stock dividends, included in accrued liabilities in the Company’s balance sheets, and $24,000 and $24,000 of accrued dividends were recorded during the years ended December 31, 2021 and 2020, respectively. 2) Voting Rights. Shares of the Series A Convertible Preferred Stock have no voting rights. However, so long as any shares of Series A Convertible Preferred Stock are outstanding, the Company may not, without the affirmative vote of the holders of the shares of Series A Convertible Preferred Stock then outstanding, (a) adversely change the powers, preferences or rights given to the Series A Convertible Preferred Stock, (b) authorize or create any class of stock senior or equal to the Series A Convertible Preferred Stock, (c) amend its certificate of incorporation or other charter documents, so as to affect adversely any rights of the holders of Series A Convertible Preferred Stock or (d) increase the authorized number of shares of Series A Convertible Preferred Stock. 3) Liquidation. Upon any liquidation, dissolution or winding-up of the Company, the holders of the Series A Convertible Preferred Stock are entitled to receive an amount equal to the Stated Value per share, which is currently $10 per share plus any accrued and unpaid dividends. 4) Conversion Rights. Each share of Series A Convertible Preferred Stock is convertible at the option of the holder into that number of shares of common stock determined by dividing the Stated Value, currently $10 per share, by the conversion price, which at the time of issuance was $928.80 per share, and subsequently adjusted to $691.20 per share. 5) Subsequent Equity Sales. The conversion price is subject to adjustment for dilutive issuances for a period of 12 months beginning March 17, 2006 and the conversion price was adjusted to $691.20 per share. 6) Automatic Conversion. If the price of the Company’s common stock equals $1,857.60 per share for 20 consecutive trading days, and an average of 116 shares of common stock per day are traded during the 20 trading days, the Company will have the right to deliver a notice to the holders of the Series A Convertible Preferred Stock, requesting the holders to convert any portion of the shares of Series A Convertible Preferred Stock into shares of common stock at the applicable conversion price. As of the date of these financial statements, such conditions have not been met. Series D Convertible Preferred Stock and Service Receivable On May 8, 2020, the Company entered into a Stock and Warrant Subscription Agreement with PoC, whereby PoC agreed to finance an additional $2.3 million for a clinical trial in exchange for (i) 602,833 shares of its common stock (the “Common Stock”), (ii) 154,670 shares of its Series D Preferred Stock and (iii) a warrant exercisable for 859,813 shares of its Common Stock. In exchange, PoC is funding our clinical development of onvansertib in metastatic colorectal cancer pursuant to a Master Services Agreement dated as of January 25, 2019, as amended. The warrant will be exercisable six months following the date of issuance at an exercise price of $1.50 per share and will expire on November 7, 2025. In June of 2020, all 154,670 Series D Preferred Stock were converted to 1,546,700 shares of Common Stock. The Company evaluated the awards issued under this transaction and determined they should be classified as equity. These equity awards were fully vested and non-forfeitable. Since the equity awards were for clinical trial services yet to be provided, the Company recognized $2.3 million service receivables as contra equity. The Company releases the service receivables as clinical trial services are performed. The conversion feature of the Series D Convertible Preferred Stock at the time of issuance was determined to be beneficial on the commitment date. Because the Series D Convertible Preferred Stock was perpetual with no stated maturity date, and the conversions could occur any time from inception, the Company immediately recorded a non-cash deemed dividend of $0.6 million related to the beneficial conversion feature arising from the issuance of Series D Convertible Preferred Stock. This non-cash deemed dividend increased the Company’s net loss attributable to common stockholders and net loss per share for the year-ending December 31, 2020. Series E Convertible Preferred Stock On June 15, 2020 the Company entered into a Securities Purchase Agreement with Acorn Bioventures LP ("Acorn"), CDK Associates, L.L.C. (“CDK”) and Third Street Holdings LLC (“Third Street”), pursuant to which the Company agreed to offer, issue and sell to Acorn, CDK and Third Street, (i) in a registered direct offering, an aggregate of 1,984,328 shares of common stock and (ii) in a concurrent private placement, (a) an aggregate of 865,824 shares of Series E Preferred Stock (“Series E Preferred Stock”) and (b) Series N warrants to purchase up to 2,213,115 shares of Common Stock. The Series E Preferred Stock is convertible at any time determined by dividing the $10 stated value per share of the Series E Preferred Stock by a conversion price of $2.44 per share, subject to adjustment in accordance with the Certificate of Designation. The Series N Warrants will be exercisable six months following the date of issuance at an exercise price of $2.39 per share and will expire on December 16, 2025. Certain investors converted 210,780 shares of Series E Convertible Preferred stock to 863,852 shares of Common Stock during December 2020. The conversion feature of the Series E Convertible Preferred Stock at the time of issuance was determined to be beneficial on the commitment date. Because the Series E Convertible Preferred Stock was perpetual with no stated maturity date, and the conversions could occur any time from inception, the Company immediately recorded a non-cash deemed dividend of $2.7 million related to the beneficial conversion feature arising from the issuance of Series E Convertible Preferred Stock. This non-cash deemed dividend increased the Company’s net loss attributable to common stockholders and net loss per share for the year-ending December 31, 2020. In conjunction with the June 15, 2020 offering, we issued 184,426 warrants as an advisory fee. These warrants are exercisable six months following the date of issuance at an exercise price of $3.05 per share and will expire 5.5 years following the date of issuance. These warrants are classified as equity and its estimated fair value of $370,666 was recognized as additional paid in capital on the issuance date. The estimated fair value is determined using the Black-Scholes Option Pricing Model which is based on the value of the underlying common stock at the valuation measurement date, the remaining contractual term of the warrant, risk-free interest rates, expected dividends and expected volatility of the price of the underlying common stock. Securities Purchase Agreements with Lincoln Park Capital Fund, LLC On March 30, 2020, the Company entered into a Securities Purchase Agreement with Lincoln Park Capital Fund, LLC ("LPC") which the company sold a combination of common stock and warrants for gross proceeds of $1.0 million. Under this agreement 800,000 shares of common stock, 131,967 pre-funded warrants and 931,967 Series J Warrants were sold. On April 9, 2020, the Company entered into a Securities Purchase Agreement with LPC, which the company sold a combination of common stock and warrants for gross proceeds of $1.1 million. Under this agreement 904,970 shares of common stock, 255,000 pre-funded warrants and 1,159,970 Series L Warrants were sold. Securities Purchase Agreement with Certain Directors and Executives On May 11, 2020 and May 14, 2020, the Company entered into Securities Purchase Agreements with certain directors and executives of the Company pursuant to which the Company sold 447,761 shares of common stock at a purchase price of $1.34 per share and 146,854 shares of common stock at a purchase price of $1.43 per share. The gross proceeds from these purchases were $810,000. Securities Purchase Agreement with Acorn Bioventures LP On May 26, 2020, the Company entered into a Securities Purchase Agreement with Acorn which the Company sold a combination of common stock and warrants for gross proceeds of $2.5 million. Under the agreement the Company sold 1,205,400 shares of common stock and 482,160 Series M Warrants. Underwritten Public Offering On October 2, 2020 the Company completed an underwritten public offering of 6,500,000 shares of its common stock at a price to the public of $13.50 per share. In addition, the underwriters exercised in full an option to purchase an additional 975,000 shares of common stock at the public offering price, less the underwriting discounts and commissions. All of the shares in the offering were sold by the Company, with gross proceeds of approximately $100.9 million, and net proceeds of approximately $94.0 million, after deducting underwriting discounts, commissions and estimated offering expenses. Sales Agreement with Jefferies LLC During May 2021, the Company sold 2.0 million shares of its common stock under the Sales Agreement with Jefferies LLC., for gross proceeds of approximately $20.0 million. Pfizer Breakthrough Growth Initiative

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation 2021 Equity Incentive Plan In June 2021 the Company's stockholders approved the 2021 Omnibus Equity Incentive Plan ("2021 Plan"). The number of authorized shares in the 2021 plan is equal to the sum of (i) 3,150,000 shares, plus (ii) the number of shares of Common Stock reserved, but unissued under the 2014 Plan; and (iii) the number of shares of Common Stock underlying forfeited awards under the 2014 Plan. As of December 31, 2021, there were 2,284,862 shares available for issuance under the 2021 Plan. 2014 Equity Incentive Plan Subsequent to the adoption of the 2021 Plan, no additional equity awards can be made under the terms of the 2014 Plan. Inducement Grants In July 2021, the Company began issuing equity awards to certain new employees as inducement grants outside of its 2021 Plan. As of December 31, 2021, an aggregate of 790,112 shares were issuable upon the exercise of inducement grant stock options approved by the Company. Modification of Stock Options In June 2021 two of the Company's directors' terms ended. At the conclusion of their term, the Compensation Committee passed a resolution to extend the expiration date of the departing directors vested stock options, and to immediately accelerate the vesting of one of the directors unvested options. The Company recorded incremental stock compensation expenses of $0.6 million during the twelve months ending December 31, 2021, related to the modifications. Stock-based compensation has been recognized in operating results as follows: (in thousands) Years ended December 31, 2021 2020 Research and development expenses 491 355 Selling, general and administrative expenses 2,743 1,410 Total stock-based compensation $ 3,234 $ 1,765 Stock Options The estimated fair value of stock option awards was determined on the date of grant using the Black-Scholes option valuation model with the following assumptions during the years indicated below: Years ended December 31, 2021 2020 Risk-free interest rate 0.83% - 1.3% 0.39% - 0.93% Dividend yield 0% 0% Expected volatility (range) 107% - 110% 102% - 106% Expected volatility (weighted-average) 108% 105% Expected term (in years) 6.0 years 5.9 years Risk-free interest rate — Based on the daily yield curve rates for U.S. Treasury obligations with maturities that correspond to the expected term of the Company’s stock options. Dividend yield — Cardiff Oncology has not paid any dividends on common stock since its inception and does not anticipate paying dividends on its common stock in the foreseeable future. Expected volatility — Based on the historical volatility of Cardiff Oncology’s common stock. Expected term — The expected option term represents the period that stock-based awards are expected to be outstanding based on the simplified method, which averages an award’s weighted-average vesting period and expected term for “plain vanilla” share options. Options are considered to be “plain vanilla” if they have the following basic characteristics: (1) are granted “at-the-money”; (2) exercisability is conditioned upon service through the vesting date; (3) termination of service prior to vesting results in forfeiture; (4) limited exercise period following termination of service; and (5) are non-transferable and non-hedgeable. Forfeitures — The Company estimates forfeitures based on its historical experience. The weighted-average fair value per share of all options granted during the years ended December 31, 2021 and 2020, estimated as of the grant date using the Black-Scholes option valuation model, was $5.96 and $2.09 per share, respectively. The unrecognized compensation cost related to non-vested stock options outstanding at December 31, 2021 was $10.1 million. The weighted-average remaining amortization period at December 31, 2021 for non-vested stock options was 3.2 years. The total fair value of shares vested during the years ended December 31, 2021 and 2020 was $1.2 million and $1.5 million, respectively. The intrinsic value of stock options exercised during the year ended December 31, 2020 was $1.0 million. A summary of stock option activity and of changes in stock options outstanding is presented below: Number of Options Weighted-Average Exercise Price Per Share Intrinsic Weighted-Average Balance outstanding, December 31, 2020 1,860,507 $ 7.43 $ 27,963,363 8.9 years Granted 1,926,466 $ 7.27 Forfeited (10,770) $ 2.55 Expired (4,219) $ 216.00 Balance outstanding, December 31, 2021 3,771,984 $ 7.13 $ 6,405,258 8.7 years Vested and exercisable, December 31, 2021 1,281,604 $ 8.96 $ 4,303,588 7.6 years Vested and expected to vest, December 31, 2021 3,671,664 $ 7.18 $ 6,253,298 8.7 years Restricted Stock Units RSU's are measured at the grant date based on the closing market price of the Company’s common stock at the grant date and recognized ratably over the service period through the vesting date. All RSU's were granted with no purchase price. Vesting of the RSU's is generally subject to service conditions. A summary of the RSU's activity is presented below: Number of Shares Weighted Average Intrinsic Non-vested RSU's outstanding, December 31, 2019 11,301 $ 15.38 $ 14,013 Vested (10,810) $ 9.37 Non-vested RSU's outstanding, December 31, 2020 491 $ 147.60 $ 7,641 Vested (491) $ 147.60 Non-vested RSU's outstanding, December 31, 2021 — $ — $ —

Derivative Financial Instrument

Derivative Financial Instruments - Warrants	12 Months Ended
	Dec. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments - Warrants	Derivative Financial Instruments — Warrants Certain warrants issued in connection with the Company’s equity financings are accounted for as derivative liabilities. Accordingly, the warrants are remeasured at each balance sheet date based on their estimated fair value using the Black-Scholes option pricing model. Changes in fair value are recorded within Company’s statements of operations. The assumptions used to determine the fair value of the warrants using the Black-Scholes option pricing model were: As of December 31, 2021 2020 Fair value of Cardiff Oncology common stock $6.01 $17.99 Expected warrant term 1.1 years 2.1 years Risk-free interest rate 0.41 % 0.13 % Expected volatility of Cardiff Oncology common stock 83 % 116 % Dividend yield 0 % 0 % Expected volatility is based on the historical volatility of Cardiff Oncology’s common stock. The warrants have a transferability provision and based on guidance for instruments issued with such a provision, Cardiff Oncology used the remaining contractual term as the expected term of the warrants. The risk-free interest rate is based on the U.S. Treasury security rates consistent with the expected remaining term of the warrants at each balance sheet date. The following table sets forth the components of changes in the Company’s derivative financial instruments — warrants liability balance, valued using the Black-Scholes option pricing method, for the periods indicated. (in thousands, except for number of warrants) Date Description Number of Warrants Derivative December 31, 2019 Balance of derivative financial instruments — warrants liability 64,496 $ 4 Change in fair value of derivative financial instruments — warrants during the year recognized as a gain in the statement of operations — 281 December 31, 2020 Balance of derivative financial instruments — warrants liability 64,496 285 Change in fair value of derivative financial instruments — warrants during the year recognized as a loss in the statement of operations — (285) December 31, 2021 Balance of derivative financial instruments — warrants liability 64,496 $ —

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following table presents the Company’s assets and liabilities that are measured and recognized at fair value on a recurring basis classified under the appropriate level of the fair value hierarchy as of December 31, 2021 and 2020: Fair Value Measurements at (in thousands) Quoted Prices in Active Markets for Identical Assets and Liabilities Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market fund $ 10,990 $ — $ — $ 10,990 Total included in cash and cash equivalents $ 10,990 $ — $ — $ 10,990 Available for sale investments: Certificate of deposit — 1,260 — 1,260 Corporate debt securities — 88,390 — 88,390 Commercial paper — 14,454 — 14,454 Non U.S. government — 728 — 728 U.S. treasury securities 24,046 — — 24,046 Total available for sale investments (1) $ 24,046 $ 104,832 $ — $ 128,878 Total assets measured at fair value on a recurring basis $ 35,036 $ 104,832 $ — $ 139,868 Fair Value Measurements at (in thousands) Quoted Prices in Active Markets for Identical Assets and Liabilities Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market fund $ 129,988 $ — $ — $ 129,988 Total assets measured at fair value on a recurring basis $ 129,988 $ — $ — $ 129,988 Liabilities: Derivative financial instruments — warrants (2) $ — $ — $ 285 $ 285 Total liabilities measured at fair value on a recurring basis $ — $ — $ 285 $ 285 (1) Included in short-term investments in the accompanying balance sheets. (2) A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. At each reporting period, all assets and liabilities for which the fair value measurement is based on significant unobservable inputs or instruments that trade infrequently and therefore have little or no price transparency are classified as Level 3. See Note 7 to the financial statements for further information. The Company’s policy is to recognize transfers between levels of the fair value hierarchy on the date of the event or change in circumstances that caused the transfer. There were no transfers into or out of Level 3 during the years ended December 31, 2021 and 2020.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes At December 31, 2021, Cardiff Oncology had federal net operating loss carryforwards (“NOLs”) of approximately $128.9 million which, if not used, will continue to expire through 2037, and federal net operating loss carryforwards of approximately $73.3 million, which do not expire. Cardiff Oncology also has California NOLs of approximately $75.6 million which, if not used, will begin to expire in 2030. Cardiff Oncology also has research and development tax credits available for federal and California purposes of approximately $2.4 million and $2.0 million, respectively. The federal research and development tax credits will begin to expire on January 31, 2025. The California research and development tax credits do not expire. Pursuant to the Internal Revenue Code of 1986, as amended (the “Code”) Sections 382 and 383, annual use of a company’s NOL and research and development credit carryforwards may be limited if there is a cumulative change in ownership of greater than 50% within a three-year period. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. If limited, the related tax asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. The Company has not completed such an analysis pursuant to Sections 382 and 383 and has established a valuation allowance as the realization of such deferred tax assets has not met the more likely than not threshold requirement. Due to the existence of the valuation allowance, further changes in the Company’s unrecognized tax benefits will not impact the Company’s effective tax rate. The provision for income taxes based on losses from continuing operations consists of the following at December 31 (in thousands): Years ended December 31, 2021 2020 Current: State $ 1 $ 1 Total current provision 1 1 Deferred: Federal (5,551) (4,043) State (531) (92) Total deferred (benefit) expense (6,082) (4,135) Valuation allowance 6,081 4,134 Total income tax provision $ — $ — Significant components of the Company’s taxes and the rates as of December 31 are shown below (in thousands, except percentages): Years ended December 31, 2021 2020 Tax computed at the federal statutory rate $ (5,941) 21 % $ (4,054) 21 % State tax, net of federal tax benefit (233) 1 % (122) 1 % Permanent items 62 — % 261 (1) % Stock based compensation 325 (1) % 81 (1) % Tax credits (366) 1 % (300) 2 % Other 72 — % — — % Valuation allowance increase (decrease) 6,081 (22) % 4,134 (22) % Provision for income taxes $ — — % $ — — % Significant components of the Company’s deferred tax assets and liabilities from federal and state income taxes as of December 31 are shown below (in thousands): Years ended December 31, 2021 2020 Deferred tax assets: Tax loss carryforwards $ 47,902 $ 42,331 Research and development credits and other tax credits 4,035 3,904 Stock-based compensation 962 684 Other 1,750 1,116 Total deferred tax assets 54,649 48,035 Deferred tax liabilities: Operating lease right-of-use assets (611) (74) Other — (6) Total deferred tax liabilities (611) (80) Net deferred tax assets before valuation allowance 54,038 47,955 Valuation allowance (54,038) (47,955) Net deferred tax asset $ — $ — Since inception the Company has incurred continuing losses and expects to continue to incur losses for the foreseeable future. The Company has recorded a full valuation allowance against its net deferred tax assets as it is more likely than not they will not be realized. Cardiff Oncology does not have any unrecognized tax benefits. Cardiff Oncology’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense, and none have been incurred to date. The Company does not anticipate a significant change in unrecognized tax benefits over the next 12 months. The Company is subject to taxation in the U.S. and California. Due to net operating losses all tax years since inception remain open to examination.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Executive Agreements Certain executive agreements provide for severance payments in case of terminations without cause or certain change of control scenarios. Research and Development and Clinical Trial Agreements In March 2017, the Company entered into a license agreement with Nerviano which granted the Company development and commercialization rights to NMS-1286937, which Cardiff Oncology refers to as onvansertib. The Company was committed to order $1.0 million of future services provided by Nerviano, such as the cost to manufacture drug product, no later than June 30, 2019, and these services have been purchased. Terms of the agreement also provide for the Company to pay development milestones and royalties based on sales volume. The Company is a party of various agreements under which it licenses technology on an exclusive basis in the field of oncology therapeutics. These agreements include License fees, Royalties and Milestone payments. The company also has a legacy license agreement in the field of oncology diagnostics under which royalty payments are due. These royalty payments are calculated as a percent of revenue. During the years ended December 31, 2021 and 2020 payments have not been material. Litigation Cardiff Oncology does not believe that it has legal liabilities that are probable or reasonably possible that require either accrual or disclosure. From time to time, the Company may become involved in various lawsuits and legal proceedings that arise in the ordinary course of business. Litigation is subject to inherent uncertainties, and an adverse result in matters may arise from time to time that may harm the Company’s business. As of the date of this report, management believes that there are no claims against the Company, which it believes will result in a material adverse effect on the Company’s business or financial condition.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit Plan The Company has a defined contribution retirement plan under Section 401(k) of the Internal Revenue Service ("IRS") Code covering its employees. The plan allows employees to defer, up to the maximum allowed, a percentage of their income through contributions to the plan as allowed by IRS Code. The Company does not currently make matching contributions.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Leucadia Life Sciences In November 2018, the Company entered into a Material Transfer Agreement (“MTA”) with Leucadia Life Sciences (“Leucadia”) pursuant to which Leucadia developed a PCR-based assay for onvansertib for Acute Myeloid Leukemia (“AML”). This assay was completed in December 2020. During the duration of the agreement, one of the Company's directors the late Dr. Thomas Adams (who is no longer a director as of June 2021), was a principal stockholder of Leucadia. In connection with the MTA, the Company entered into a consulting agreement with Tommy Adams, Co-Founder & Chief Operating Officer of Leucadia, who is the son of Dr. Adams. During the years ended December 31, 2021 and 2020, the Company incurred and recorded approximately $0.0 million and $1.1 million, respectively, of research and development expenses for services performed by Leucadia and Tommy Adams. Gary Pace Securities Purchase Agreement

COVID-19

COVID-19	12 Months Ended
	Dec. 31, 2021
Unusual or Infrequent Items, or Both [Abstract]
COVID-19	COVID-19 The COVID-19 outbreak in the United States has caused significant business disruption. Thus far COVID-19 has not caused material disruptions to the Company's operational and financial performance. A prolonged outbreak could have a material adverse impact on financial results and business operations of the Company, including the timing and ability of the Company to complete certain clinical trials and other efforts required to advance the development of its drugs and raise additional capital. Repayment of Small Business Administration Payroll Protection Program Loan On April 15, 2020, the Company was granted a loan (the “Loan”) from JPMorgan Chase Bank, N.A. in the aggregate amount of $305,000, pursuant to the Paycheck Protection Program (the “PPP”) under Division A, Title I of the CARES Act with an interest rate of 0.98% per annum. On October 19, 2020 the Company repaid in full the outstanding principal and interest of the PPP Loan.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsConversion of Series E Convertible Preferred Stock327,535 Series E Convertible Preferred Shares were converted into 1,342,357 shares of common stock on January 5, 2022.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations as, and manages its business in, one operating segment.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make significant estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The most significant estimate involves accrued clinical trial expenses.
Accrued Clinical Trial Expenses	Accrued Clinical Trial Expenses The Company expenses research and development expenditures as incurred, which include costs related to clinical trial activities. The Company accrues costs for clinical trial activities based upon estimates of the services received and related expenses incurred that have yet to be invoiced by the Clinical Research Organizations ("CROs"), investigators, professional service providers, and other vendors providing clinical trial services (collectively, the “service providers”). As of December 31, 2021 the Company’s clinical trial accrual balance of $1.6 million is included in accrued liabilities. The Company’s related 2021 clinical trial expenses are included in research and development expense of $17.4 million. Certain clinical trial expenses are released from service receivables classified within equity (see Note 5) as clinical trial services are performed.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents consist of cash in readily available checking and money market accounts. Investment Securities All investments have been classified as “available-for-sale” and are carried at fair value as determined based upon quoted market prices or pricing models for similar securities at period end. Investments with contractual maturities less than 12 months at the balance sheet date are considered short-term investments. Investments with contractual maturities beyond one year are also classified as short-term due to the Company’s ability to liquidate the investment for use in operations within the next 12 months. Realized gains and losses on investment securities are included in earnings and are derived using the specific identification method for determining the cost of securities sold. The Company has not realized any significant gains or losses on sales of available-for-sale investment securities during any of the periods presented. As all the Company’s investment holdings are in the form of debt securities or certificates of deposit, unrealized gains and losses that are determined to be temporary in nature are reported as a component of accumulated other comprehensive loss. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. Interest income is recognized when earned and is included in investment income, as are the amortization of purchase premiums and accretion of purchase discounts on investment securities.
Concentration of Credit Risk	Concentration of Credit Risk
Revenues	Revenues The Company recognizes revenue when control of its products and services are transferred to its customers in an amount that reflects the consideration it expects to receive from its customers in exchange for those products and services. This process involves identifying the contract with a customer, determining the performance obligations in the contract, determining the contract price, allocating the contract price to the distinct performance obligations in the contract, and recognizing revenue when the performance obligations have been satisfied. A performance obligation is considered distinct from other obligations in a contract when it provides a benefit to the customer either on its own or together with other resources that are readily available to the customer and is separately identified in the contract. The Company considers a performance obligation satisfied once it has transferred control of goods or service to the customer, meaning the customer has the ability to use and obtain the benefit of goods or service. The Company recognizes revenue for satisfied performance obligations only when it determines there are no uncertainties regarding payment terms or transfer of control. For sales-based royalties, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Royalty and License Revenues The Company licenses and sublicenses its patent rights to healthcare companies, medical laboratories and biotechnology partners. These patents are from the Company's legacy portfolio and unrelated to onvasertib. Agreements may involve multiple elements such as license fees, minimum royalties, usage-based royalties and milestone payments. Revenue is recognized when the criteria described above have been met as well as the following: • Up-front nonrefundable license fees pursuant to agreements under which the Company has no continuing performance obligations are recognized as revenues on the effective date of the agreement and when collection is probable. • Minimum royalties are recognized as earned, and royalties are earned based on the licensee’s use. The Company estimates and records licensee’s sales based on historical usage rate and collectability. • For sales-based royalties, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied).
Derivative Financial Instruments—Warrants	Derivative Financial Instruments—Warrants The Company has issued common stock warrants in connection with the execution of certain equity financings. Such warrants are classified as derivative liabilities and are recorded at their fair market value as of each reporting period as they do not meet the criteria for equity classification. Changes in fair value of derivative liabilities are recorded in the statement of operations under the caption “Change in fair value of derivative instruments — warrants.” The fair value of warrants is determined using the Black-Scholes option-pricing model using assumptions regarding the historical volatility of Cardiff Oncology’s common stock price, the remaining life of the warrants, and the risk-free interest rates at each period end. The Company thus uses model-derived valuations where inputs are observable in active markets to determine the fair value. The use of the Black-Scholes model classifies such warrants as Level 3 (See " Fair Value of Financial Instruments"
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense is measured at the grant date based on the estimated fair value of the award and is recognized straight-line over the requisite service period of the individual grants, which typically equals the vesting period.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Financial instruments consist of cash equivalents, accounts receivable, accounts payable and derivative liabilities. The Company applies ASC 820 for financial assets and liabilities that are required to be measured at fair value and non-financial assets and liabilities that are not required to be measured at fair value on a recurring basis. These financial instruments are stated at their respective historical carrying amounts, which approximate fair value due to their short-term nature as they reflect current market interest rates. The authoritative guidance establishes a fair value hierarchy that is based on the extent and level of judgment used to estimate the fair value of assets and liabilities. In general, the authoritative guidance requires us to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. An asset or liability’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the measurement of its fair value. The three levels of input defined by the authoritative guidance are as follows: The Company measures certain assets and liabilities at fair value on a recurring basis using the three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. The three tiers include: • Level 1 — Quoted prices for identical instruments in active markets. • Level 2 — Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations where inputs are observable or where significant value drivers are observable. • Level 3 — Instruments where significant value drivers are unobservable to third parties.
Long-Lived Assets	Long-Lived Assets Long-lived assets consist of property, equipment and lease right-of-use assets. The Company records property and equipment at cost. Depreciation on property and equipment is calculated using the straight-line method over the estimated useful life of the asset. Depreciation of leasehold improvements is computed based on the shorter of the life of the asset or the term of the lease. The estimated useful lives of the major classes of property and equipment are as follows: Estimated Useful Lives Furniture and office equipment 3 to 5 years Leasehold improvements 5 to 6 years Laboratory equipment 5 years
Impairment Losses on Long-Lived Assets	Impairment losses on long-lived assets used in operations are recorded when indicators of impairment are present and the undiscounted cash flows estimated to be generated by those assets are less than the assets carrying amount. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the estimated fair value of the assets.
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease Right-of-Use (“ROU”) assets, current operating lease liabilities and non-current operating lease liabilities in the Company’s balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. None of the Company’s operating leases provide an implicit rate, therefore the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The incremental borrowing rate is the rate of interest that the Company would expect to pay to borrow on a collateralized and fully amortizing basis over a similar term an amount equal to the lease payments in a similar economic environment. The operating lease ROU asset also includes any lease payments made less lease incentives received. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. Our facilities lease agreement contains lease and non-lease components, such as common area maintenance. We have elected to account for these lease and non-lease components of this agreement as a single lease component.
Income Taxes	Income Taxes Income taxes are determined using the asset and liability approach of accounting for income taxes. Under this approach, deferred taxes represent the future tax consequences expected to occur when the reported amounts of assets and liabilities are recovered or paid. Deferred taxes result from differences between the financial statement and tax bases of Cardiff Oncology’s assets and liabilities and are adjusted for changes in tax rates and tax laws when changes are enacted. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized. The assessment of whether or not a valuation allowance is required often requires significant judgment.
Contingencies	Contingencies In the normal course of business, Cardiff Oncology is subject to loss contingencies, such as legal proceedings and claims arising out of its business, that cover a wide range of matters, including, among others, government investigations, stockholder lawsuits, product and environmental liability, and tax matters. In accordance with FASB ASC Topic 450, Contingencies , Cardiff Oncology records such loss contingencies when it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. Cardiff Oncology, in accordance with this guidance, does not recognize gain contingencies until realized.
Research and Development	Research and Development Research and development expenses include expenditures in connection with an in-house research and development laboratory, salaries and staff costs, clinical trials, purchased in-process research and development and regulatory and scientific consulting fees, as well as contract research and insurance. Also, patent filing and patent maintenance expenses are considered legal in nature and therefore classified as general and administrative expense, if any.
Net Loss Per Share	Net Loss Per Share
Recent Accounting Pronouncement Not Yet Adopted	Recent Accounting Pronouncement Not Yet Adopted In August 2020, the FASB issued ASU No. 2020-06 ("ASU 2020-06"), Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). ASU 2020-06 eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, ASU 2020-06 modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2021 (or December 15, 2023 for companies who meet the SEC definition of Smaller Reporting Companies), and interim periods within those fiscal years. The amendment is to be adopted through either a fully retrospective or modified retrospective method of transition. Early adoption is permitted. The Company is currently evaluating the impact of this standard on its financial statements and related disclosures. In May 2021, the FASB issued ASU No. 2021-04 ("ASU 2021-04), Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation—Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options (a consensus of the FASB Emerging Issues Task Force). The amendments in this update are effective for all entities for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. The Company will adopt this standard on January 1, 2022 and does not expect that the adoption of this standard will have a material impact on its financial statements and related disclosures.

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Useful Life of Property and Equipment	The estimated useful lives of the major classes of property and equipment are as follows: Estimated Useful Lives Furniture and office equipment 3 to 5 years Leasehold improvements 5 to 6 years Laboratory equipment 5 years As of December 31, (in thousands) 2021 2020 Furniture and office equipment $ 955 $ 798 Leasehold improvements 1,962 1,962 Laboratory equipment 906 868 3,823 3,628 Less—accumulated depreciation (3,441) (3,004) Property and equipment, net $ 382 $ 624
Schedule of Antidilutive Securities Excluded from the Calculation of Basic and Diluted Loss Per Share	Shares used in calculating diluted net loss per common share exclude as anti-dilutive the following share equivalents: December 31, 2021 2020 Options to purchase Common Stock 3,771,984 1,860,507 Warrants to purchase Common Stock 4,490,159 5,260,992 Restricted Stock Units — 491 Series A Convertible Preferred Stock 877 877 Series E Convertible Preferred Stock 2,684,607 2,684,607 10,947,627 9,807,474

Supplementary Balance Sheet I_2

Supplementary Balance Sheet Information (Tables)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Components of Short-term investments	Short-term investments available-for-sale securities consist of the following: As of December 31, 2021 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Maturity less than 1 year: Certificate of deposit $ 1,260 $ — $ — $ 1,260 Corporate debt securities 58,822 2 (38) 58,786 Commercial paper 14,453 4 (3) 14,454 Non U.S. government 728 — — 728 U.S. treasury securities 20,380 — (24) 20,356 Total maturity less than 1 year 95,643 6 (65) 95,584 Maturity 1 to 2 years: Corporate debt securities 29,676 1 (73) 29,604 U.S. treasury securities 3,701 — (11) 3,690 Total maturity 1 to 2 years 33,377 1 (84) 33,294 Total short-term investments $ 129,020 $ 7 $ (149) $ 128,878
Components of Property and Equipment	The estimated useful lives of the major classes of property and equipment are as follows: Estimated Useful Lives Furniture and office equipment 3 to 5 years Leasehold improvements 5 to 6 years Laboratory equipment 5 years As of December 31, (in thousands) 2021 2020 Furniture and office equipment $ 955 $ 798 Leasehold improvements 1,962 1,962 Laboratory equipment 906 868 3,823 3,628 Less—accumulated depreciation (3,441) (3,004) Property and equipment, net $ 382 $ 624
Components of Accrued Liabilities	Accrued liabilities consisted of the following: As of December 31, (in thousands) 2021 2020 Accrued compensation $ 1,435 $ 1,523 Preferred stock dividend 414 390 Clinical trials 1,639 1,557 Research agreements and services 726 67 Director fees 141 93 Professional fees and outside services 63 38 Patent, license and other fees 43 117 Other accrued liabilities 66 66 Total accrued liabilities $ 4,527 $ 3,851

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Summary of Lease Expense and Supplemental Cash Flow Information	The components of lease expense were as follows: (in thousands) Twelve Months Ended December 31, 2021 Twelve Months Ended December 31, 2020 Operating lease cost $ 745 $ 441 Operating sublease income (403) (291) Net operating lease cost $ 342 $ 150 Supplemental cash flow and other information related to leases was as follows: (in thousands) Twelve Months Ended December 31, 2021 Twelve Months Ended December 31, 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 949 $ 944 ROU assets obtained in exchange for lease obligations: Operating leases $ 3,061 $ —
Supplemental Balance Sheet Information	Supplemental balance sheet information related to leases was as follows: (in thousands) As of December 31, 2021 As of December 31, 2020 Operating lease ROU assets $ 2,796 $ 343 Current operating lease liabilities $ 551 $ 860 Non-current operating lease liabilities 2,568 9 Total operating lease liabilities $ 3,119 $ 869 Weighted-average remaining lease term–operating leases 5.2 years 1.0 year Weighted-average discount rate–operating leases 7 % 6.5 %
Summary of Future Minimum Lease Payments	Total remaining annual commitments under non-cancelable lease agreements for each of the years ended December 31 are as follows: (in thousands) Year Ending December 31, Operating Leases 2022 551 2023 737 2024 754 2025 775 2026 796 Thereafter 136 Total future minimum lease payments $ 3,749 Less imputed interest (630) Total $ 3,119

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Stockholders' Equity Note [Abstract]
Summary of Warrant Activity and Changes in Warrants Outstanding	A summary of warrant activity and changes in warrants outstanding, including both liability and equity classifications, is presented below: Number of Weighted-Average Weighted-Average Remaining Contractual Term Balance outstanding, December 31, 2019 10,589,482 $ 4.08 3.7 years Granted 5,831,451 $ 1.70 Exercised (11,159,941) $ 2.31 Balance outstanding, December 31, 2020 5,260,992 $ 5.19 4.1 years Exercised (770,833) $ 1.64 Balance outstanding, December 31, 2021 4,490,159 $ 5.80 3.0 years The above table excludes pre-funded warrants with a nominal exercise price of $.01 per share: 1. 605,072 pre-funded warrants outstanding as of December 31, 2019; 2. 386,967 pre-funded warrants which were issued during the twelve months ending December 31, 2020; 3. All 992,039 pre-funded warrants were exercised in full during the twelve months ending December 31, 2020.
Schedule of Preferred Stock	A summary of our Company's classes of preferred stock is presented below: Shares outstanding Class Par value Shares designated Liquidation preference As of December 31, 2021 As of December 31, 2020 Series A Convertible Preferred Stock $ 0.001 277,100 $ 606,000 60,600 60,600 Series B Convertible Preferred Stock $ 0.001 8,860 None — — Series C Convertible Preferred Stock $ 0.001 200,000 None — — Series D Convertible Preferred Stock $ 0.0001 154,670 None — — Series E Convertible Preferred Stock $ 0.001 865,824 None 655,044 655,044

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-based compensation recognized	Stock-based compensation has been recognized in operating results as follows: (in thousands) Years ended December 31, 2021 2020 Research and development expenses 491 355 Selling, general and administrative expenses 2,743 1,410 Total stock-based compensation $ 3,234 $ 1,765
Estimated Fair Value of Stock Options - Assumptions	The estimated fair value of stock option awards was determined on the date of grant using the Black-Scholes option valuation model with the following assumptions during the years indicated below: Years ended December 31, 2021 2020 Risk-free interest rate 0.83% - 1.3% 0.39% - 0.93% Dividend yield 0% 0% Expected volatility (range) 107% - 110% 102% - 106% Expected volatility (weighted-average) 108% 105% Expected term (in years) 6.0 years 5.9 years
Summary of Stock Option Activity	A summary of stock option activity and of changes in stock options outstanding is presented below: Number of Options Weighted-Average Exercise Price Per Share Intrinsic Weighted-Average Balance outstanding, December 31, 2020 1,860,507 $ 7.43 $ 27,963,363 8.9 years Granted 1,926,466 $ 7.27 Forfeited (10,770) $ 2.55 Expired (4,219) $ 216.00 Balance outstanding, December 31, 2021 3,771,984 $ 7.13 $ 6,405,258 8.7 years Vested and exercisable, December 31, 2021 1,281,604 $ 8.96 $ 4,303,588 7.6 years Vested and expected to vest, December 31, 2021 3,671,664 $ 7.18 $ 6,253,298 8.7 years
Summary of Restricted Stock Unit Activity	A summary of the RSU's activity is presented below: Number of Shares Weighted Average Intrinsic Non-vested RSU's outstanding, December 31, 2019 11,301 $ 15.38 $ 14,013 Vested (10,810) $ 9.37 Non-vested RSU's outstanding, December 31, 2020 491 $ 147.60 $ 7,641 Vested (491) $ 147.60 Non-vested RSU's outstanding, December 31, 2021 — $ — $ —

Derivative Financial Instrume_2

Derivative Financial Instruments - Warrants (Tables) - Black Scholes Option Pricing Method	12 Months Ended
	Dec. 31, 2021
Derivative financial instruments
Schedule of Assumptions Used to Determine the Fair Value of Warrants	The assumptions used to determine the fair value of the warrants using the Black-Scholes option pricing model were: As of December 31, 2021 2020 Fair value of Cardiff Oncology common stock $6.01 $17.99 Expected warrant term 1.1 years 2.1 years Risk-free interest rate 0.41 % 0.13 % Expected volatility of Cardiff Oncology common stock 83 % 116 % Dividend yield 0 % 0 %
Schedule of Components of Changes in the Company’s Derivative Financial Instruments Liability Balance	The following table sets forth the components of changes in the Company’s derivative financial instruments — warrants liability balance, valued using the Black-Scholes option pricing method, for the periods indicated. (in thousands, except for number of warrants) Date Description Number of Warrants Derivative December 31, 2019 Balance of derivative financial instruments — warrants liability 64,496 $ 4 Change in fair value of derivative financial instruments — warrants during the year recognized as a gain in the statement of operations — 281 December 31, 2020 Balance of derivative financial instruments — warrants liability 64,496 285 Change in fair value of derivative financial instruments — warrants during the year recognized as a loss in the statement of operations — (285) December 31, 2021 Balance of derivative financial instruments — warrants liability 64,496 $ —

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Company’s Assets and Liabilities that are Measured and Recognized at Fair Value on a Recurring Basis Classified Under the Appropriate Level of the Fair Value Hierarchy	The following table presents the Company’s assets and liabilities that are measured and recognized at fair value on a recurring basis classified under the appropriate level of the fair value hierarchy as of December 31, 2021 and 2020: Fair Value Measurements at (in thousands) Quoted Prices in Active Markets for Identical Assets and Liabilities Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market fund $ 10,990 $ — $ — $ 10,990 Total included in cash and cash equivalents $ 10,990 $ — $ — $ 10,990 Available for sale investments: Certificate of deposit — 1,260 — 1,260 Corporate debt securities — 88,390 — 88,390 Commercial paper — 14,454 — 14,454 Non U.S. government — 728 — 728 U.S. treasury securities 24,046 — — 24,046 Total available for sale investments (1) $ 24,046 $ 104,832 $ — $ 128,878 Total assets measured at fair value on a recurring basis $ 35,036 $ 104,832 $ — $ 139,868 Fair Value Measurements at (in thousands) Quoted Prices in Active Markets for Identical Assets and Liabilities Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market fund $ 129,988 $ — $ — $ 129,988 Total assets measured at fair value on a recurring basis $ 129,988 $ — $ — $ 129,988 Liabilities: Derivative financial instruments — warrants (2) $ — $ — $ 285 $ 285 Total liabilities measured at fair value on a recurring basis $ — $ — $ 285 $ 285 (1) Included in short-term investments in the accompanying balance sheets. (2) A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. At each reporting period, all assets and liabilities for which the fair value measurement is based on significant unobservable inputs or instruments that trade infrequently and therefore have little or no price transparency are classified as Level 3. See Note 7 to the financial statements for further information.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Provision for Income Taxes Based on Losses from Continuing Operations	The provision for income taxes based on losses from continuing operations consists of the following at December 31 (in thousands): Years ended December 31, 2021 2020 Current: State $ 1 $ 1 Total current provision 1 1 Deferred: Federal (5,551) (4,043) State (531) (92) Total deferred (benefit) expense (6,082) (4,135) Valuation allowance 6,081 4,134 Total income tax provision $ — $ —
Schedule of Significant Components of the Company’s Taxes and the Rates	Significant components of the Company’s taxes and the rates as of December 31 are shown below (in thousands, except percentages): Years ended December 31, 2021 2020 Tax computed at the federal statutory rate $ (5,941) 21 % $ (4,054) 21 % State tax, net of federal tax benefit (233) 1 % (122) 1 % Permanent items 62 — % 261 (1) % Stock based compensation 325 (1) % 81 (1) % Tax credits (366) 1 % (300) 2 % Other 72 — % — — % Valuation allowance increase (decrease) 6,081 (22) % 4,134 (22) % Provision for income taxes $ — — % $ — — %
Schedule of Significant Components of the Company’s Deferred Tax Assets	Significant components of the Company’s deferred tax assets and liabilities from federal and state income taxes as of December 31 are shown below (in thousands): Years ended December 31, 2021 2020 Deferred tax assets: Tax loss carryforwards $ 47,902 $ 42,331 Research and development credits and other tax credits 4,035 3,904 Stock-based compensation 962 684 Other 1,750 1,116 Total deferred tax assets 54,649 48,035 Deferred tax liabilities: Operating lease right-of-use assets (611) (74) Other — (6) Total deferred tax liabilities (611) (80) Net deferred tax assets before valuation allowance 54,038 47,955 Valuation allowance (54,038) (47,955) Net deferred tax asset $ — $ —

Business Overview and Liquidi_2

Business Overview and Liquidity (Details) $ in Millions	Dec. 31, 2021USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash, cash equivalents and short-term investments	$ 140.8

Basis of Presentation and Sum_4

Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)segment
Accounting Policies [Abstract]
Number of operating segments | segment	1
Accrued Clinical Trial Expenses	$ 1.6
Research and development expense	$ 17.4
Payment terms	Payment terms and conditions vary by contracts, although terms generally include a requirement of payment within 30 to 45 days after invoice.

Basis of Presentation and Sum_5

Basis of Presentation and Summary of Significant Accounting Policies - Warrants (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative financial instruments
Derivative financial instruments—warrants	$ 0	$ 285
Warrants to purchase Common Stock | Black Scholes Option Pricing Method
Derivative financial instruments
Derivative financial instruments—warrants	$ 0	$ 285	$ 4

Basis of Presentation and Sum_6

Basis of Presentation and Summary of Significant Accounting Policies - Long-Lived Assets (Details)	12 Months Ended
	Dec. 31, 2021
Furniture and office equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Furniture and office equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	6 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years

Basis of Presentation and Sum_7

Basis of Presentation and Summary of Significant Accounting Policies - Anti-dilutive Share Equivalents (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Net Loss Per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	10,947,627	9,807,474
Options to purchase Common Stock
Net Loss Per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	3,771,984	1,860,507
Warrants to purchase Common Stock
Net Loss Per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	4,490,159	5,260,992
Restricted Stock Units
Net Loss Per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	0	491
Series A Convertible Preferred Stock
Net Loss Per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	877	877
Series E Convertible Preferred Stock
Net Loss Per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	2,684,607	2,684,607

Supplementary Balance Sheet I_3

Supplementary Balance Sheet Information - Short-term Investments (Details)	12 Months Ended
	Dec. 31, 2021USD ($)
Maturity less than 1 year:
Amortized Cost	$ 95,643,000
Gross Unrealized Gains	6,000
Gross Unrealized Losses	(65,000)
Fair Market Value	95,584,000
Maturity 1 to 2 years:
Amortized Cost	33,377,000
Gross Unrealized Gains	1,000
Gross Unrealized Losses	(84,000)
Fair Market Value	33,294,000
Amortized Cost	129,020,000
Gross Unrealized Gains	7,000
Gross Unrealized Losses	(149,000)
Fair Market Value	128,878,000
Realized loss	0
Certificate of deposit
Maturity less than 1 year:
Amortized Cost	1,260,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Market Value	1,260,000
Corporate debt securities
Maturity less than 1 year:
Amortized Cost	58,822,000
Gross Unrealized Gains	2,000
Gross Unrealized Losses	(38,000)
Fair Market Value	58,786,000
Maturity 1 to 2 years:
Amortized Cost	29,676,000
Gross Unrealized Gains	1,000
Gross Unrealized Losses	(73,000)
Fair Market Value	29,604,000
Commercial paper
Maturity less than 1 year:
Amortized Cost	14,453,000
Gross Unrealized Gains	4,000
Gross Unrealized Losses	(3,000)
Fair Market Value	14,454,000
Non U.S. government
Maturity less than 1 year:
Amortized Cost	728,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Market Value	728,000
U.S. treasury securities
Maturity less than 1 year:
Amortized Cost	20,380,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(24,000)
Fair Market Value	20,356,000
Maturity 1 to 2 years:
Amortized Cost	3,701,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(11,000)
Fair Market Value	$ 3,690,000

Supplementary Balance Sheet I_4

Supplementary Balance Sheet Information - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 500	$ 500
Property and equipment	3,823	3,628
Less—accumulated depreciation	(3,441)	(3,004)
Property and equipment, net	382	624
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment	955	798
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	1,962	1,962
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 906	$ 868

Supplementary Balance Sheet I_5

Supplementary Balance Sheet Information - Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued compensation	$ 1,435	$ 1,523
Preferred stock dividend	414	390
Clinical trials	1,639	1,557
Clinical trials	726	67
Director fees	141	93
Professional fees and outside services	63	38
Patent, license and other fees	43	117
Other accrued liabilities	66	66
Total accrued liabilities	$ 4,527	$ 3,851

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Thousands	Jan. 01, 2022ft²	Dec. 31, 2022USD ($)	Dec. 31, 2021USD ($)ft²lease	Feb. 28, 2027
Lessee, Lease, Description [Line Items]
Number of subleases | lease			3
Area of lease occupied by company			9,500
Area of lease			26,100
Area of sublease			16,600
Monthly rent payments | $			$ 80
Forecast
Lessee, Lease, Description [Line Items]
Lease not yet commenced, area	12,300
Monthly rent payments | $		$ 55
Annual rent increase, percentage				3.00%

Leases - Lease Expense (Details

Leases - Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease cost	$ 745	$ 441
Operating sublease income	(403)	(291)
Net operating lease cost	$ 342	$ 150

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease right-of-use assets	$ 2,796	$ 343
Current operating lease liabilities	551	860
Non-current operating lease liabilities	2,568	9
Total operating lease liabilities	$ 3,119	$ 869
Weighted-average remaining lease term–operating leases	5 years 2 months 12 days	1 year
Weighted-average discount rate–operating leases	7.00%	6.50%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating cash flows from operating leases	$ 949	$ 944
ROU assets obtained in exchange for lease obligations	$ 3,061	$ 0

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating Leases
2022	$ 551
2023	737
2024	754
2025	775
2026	796
Thereafter	136
Total future minimum lease payments	3,749
Less imputed interest	(630)
Total	$ 3,119	$ 869

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Warrants (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 15, 2020
Number of Warrants
Balance of warrants outstanding at the beginning of the period (in shares)	5,260,992	10,589,482
Granted (in shares)		5,831,451
Exercised (in shares)	(770,833)	(11,159,941)
Balance of warrants outstanding at the end of the period (in shares)	4,490,159	5,260,992	10,589,482
Weighted-Average Exercise Price Per Share
Weighted average exercise price of warrants at the beginning of the period (in dollars per share)	$ 5.19	$ 4.08
Granted (in dollars per share)		1.70
Exercised (in dollars per share)	1.64	2.31
Weighted average exercise price of warrants at the end of the period (in dollars per share)	$ 5.80	$ 5.19	$ 4.08
Weighted-Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term	3 years	4 years 1 month 6 days	3 years 8 months 12 days
Exercise price of warrants (in dollars per share)	$ 0.01			$ 3.05
Pre-Funded Warrants
Number of Warrants
Balance of warrants outstanding at the beginning of the period (in shares)	605,072
Granted (in shares)	386,967
Exercised (in shares)	(992,039)
Balance of warrants outstanding at the end of the period (in shares)		605,072

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Preferred Stock (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Jun. 15, 2020
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.001
Preferred stock, shares authorized (in shares)	277,100
Series A Convertible Preferred Stock, liquidation preference	$ 606,000
Preferred stock, shares outstanding (in shares)	60,600	60,600
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.001
Preferred stock, shares authorized (in shares)	8,860
Preferred stock, shares outstanding (in shares)	0	0
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.001
Preferred stock, shares authorized (in shares)	200,000
Preferred stock, shares outstanding (in shares)	0	0
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.0001
Preferred stock, shares authorized (in shares)	154,670
Preferred stock, shares outstanding (in shares)	0	0
Series E Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.001		$ 10
Preferred stock, shares authorized (in shares)	865,824
Preferred stock, shares outstanding (in shares)	655,044	655,044

Stockholders' Equity - Series A

Stockholders' Equity - Series A Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 17, 2006	Sep. 30, 2006	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Accrued dividend during the period			$ 24	$ 24
Accumulated Deficit
Class of Stock [Line Items]
Accrued dividend during the period			$ 24	24
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Cumulative dividend rate (as a percent)			4.00%
Accrued cumulative unpaid preferred stock dividends			$ 414	$ 390
Stated value (in dollars per share)			$ 10
Conversion price per share (in dollars per share)	$ 691.20	$ 928.80	691.20
Period during which the conversion price is subject to adjustment for dilutive issuances	12 months
Share price for 20 consecutive trading days for automatic conversion			$ 1,857.6
Number of consecutive trading days in which the closing price of the entity's common stock must equal or exceed a specified price in order for the preferred stock to be automatically converted			20 days
Number of common stock shares traded per day during the 20 trading days for the preferred stock to be automatically converted			116
Number of trading days in which the specified volume of common stock must be traded for the preferred stock to be automatically converted			20 days

Stockholders' Equity - Series D

Stockholders' Equity - Series D Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 15, 2020	May 08, 2020	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Number of shares called by warrants (in shares)	2,213,115
Months until exercisable	6 months	6 months
Exercise price of warrants (in dollars per share)	$ 3.05			$ 0.01
Conversion of stock, shares issued (in shares)			1,546,700
Service receivable				$ 139	$ 2,171
Deemed dividend recognized on beneficial conversion features of convertible preferred stock	$ 2,700
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Shares converted (in shares)			154,670
Service receivable		$ 2,300
Deemed dividend recognized on beneficial conversion features of convertible preferred stock		600
Private Placement
Class of Stock [Line Items]
Amount financed under agreement		$ 2,300
Number of shares called by warrants (in shares)		859,813
Exercise price of warrants (in dollars per share)		$ 1.50
Private Placement | Common Stock
Class of Stock [Line Items]
Stock issued (in shares)		602,833
Private Placement | Series D Convertible Preferred Stock
Class of Stock [Line Items]
Stock issued (in shares)		154,670

Stockholders' Equity - Series E

Stockholders' Equity - Series E Convertible Preferred Stock (Details) - USD ($)	Oct. 02, 2020	Jun. 15, 2020	May 14, 2020	May 11, 2020	May 08, 2020	Nov. 30, 2021	May 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Sale of stock, shares issued (in shares)	6,500,000		146,854	447,761		2,400,000	2,000,000
Number of shares called by warrants (in shares)		2,213,115
Preferred stock, par value (in dollars per share)								$ 0.001	$ 0.001	$ 0.001
Months until exercisable		6 months			6 months
Exercise price of warrants (in dollars per share)		$ 3.05							0.01
Shares issued upon conversion (in shares)								863,852		863,852
Class Of Warrant Or Right, Issued		184,426
Deemed dividend recognized on beneficial conversion features of convertible preferred stock		$ 2,700,000
Expiration term		5 years 6 months
Warrants, Fair Value		$ 370,666								$ 400,000
Series N Warrant
Class of Stock [Line Items]
Months until exercisable		6 months
Exercise price of warrants (in dollars per share)		$ 2.39
Series E Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)		10							$ 0.001
Conversion price (in dollars per share)		$ 2.44
Shares converted (in shares)								210,780
Deemed dividend recognized on beneficial conversion features of convertible preferred stock									$ 0	$ 2,665,000
Registered Direct Offering
Class of Stock [Line Items]
Sale of stock, shares issued (in shares)		1,984,328
Private Placement
Class of Stock [Line Items]
Number of shares called by warrants (in shares)					859,813
Exercise price of warrants (in dollars per share)					$ 1.50
Private Placement | Series E Convertible Preferred Stock
Class of Stock [Line Items]
Sale of stock, shares issued (in shares)		865,824

Stockholders' Equity - Securiti

Stockholders' Equity - Securities Purchase Agreements (Details) - USD ($) $ / shares in Units, $ in Thousands

Oct. 02, 2020

May 26, 2020

May 14, 2020

May 14, 2020

May 11, 2020

Apr. 09, 2020

Mar. 30, 2020

Nov. 30, 2021

May 31, 2021

Dec. 31, 2021

[1]

Dec. 31, 2020

[2]

Class of Stock [Line Items]

Gross proceeds

$ 100,900

$ 2,500

$ 810

$ 1,100

$ 1,000

$ 15,000

$ 20,000

Sale of stock, shares issued (in shares)

6,500,000

146,854

447,761

2,400,000

2,000,000

Offering price (in dollars per share)

$ 13.50

$ 1.43

$ 1.43

$ 1.34

Net proceeds

$ 94,000

$ 34,187

$ 112,300

Number of days counterparty cannot sell or transfer shares

180 days

Common Stock

Class of Stock [Line Items]

Sale of stock, shares issued (in shares)

1,205,400

904,970

800,000

Over-Allotment Option

Class of Stock [Line Items]

Sale of stock, shares issued (in shares)

975,000

Pre-Funded Warrants

Class of Stock [Line Items]

Sale of stock, shares issued (in shares)

255,000

131,967

Series J Warrant

Class of Stock [Line Items]

Sale of stock, shares issued (in shares)

931,967

Series L Warrants

Class of Stock [Line Items]

Sale of stock, shares issued (in shares)

1,159,970

Series M Warrant

Class of Stock [Line Items]

Sale of stock, shares issued (in shares)

482,160

[1]

Net of expenses of $0.8 million.

[2]

Net of expenses of $7.5 million, and fair value of warrants issued as a transaction advisory fee as of the date of issuance of $0.4 million.

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	3,150,000
Incremental stock compensation	$ 0.6
Fair value of shares vested	$ 1.2	$ 1.5
Intrinsic value, exercised		$ 1
Inducement Grant Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	790,112
Options to purchase Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,926,466
Weighted average grant date fair value (in dollars per share)	$ 5.96	$ 2.09
Unrecognized compensation cost for non-vested options	$ 10.1
Period for recognition	3 years 2 months 12 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of vested awards	$ 0.1	$ 0.1
Equity Incentive Plan 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance (in shares)	2,284,862

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 3,234,000	$ 1,765,000
Research and development expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	491,000	355,000
Selling, general and administrative expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 2,743,000	$ 1,410,000

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Using Black-Scholes for Estimated Fair Value of Stock Options (Details) - Options to purchase Common Stock	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility (weighted-average)	108.00%	105.00%
Expected term (in years)	6 years	5 years 10 months 24 days
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk-free interest rate	0.83%	0.39%
Expected volatility (range)	107.00%	102.00%
Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk-free interest rate	1.30%	0.93%
Expected volatility (range)	110.00%	106.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Activity (Details) - Options to purchase Common Stock - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Options
Beginning balance (in shares)	1,860,507
Granted (in shares)	1,926,466
Forfeitures (in shares)	(10,770)
Expired (in shares)	(4,219)
Ending balance (in shares)	3,771,984	1,860,507
Vested and exercisable (in shares)	1,281,604
Vested and expected to vest (in shares)	3,671,664
Weighted-Average Exercise Price Per Share
Outstanding (in dollars per share)	$ 7.43
Granted (in dollars per share)	7.27
Forfeited (in dollars per share)	2.55
Expired (in dollars per share)	216
Outstanding (in dollars per share)	7.13	$ 7.43
Vested and exercisable (in dollars per share)	8.96
Vested and expected to vest (in dollars per share)	$ 7.18
Intrinsic value, outstanding	$ 6,405,258	$ 27,963,363
Intrinsic value, vested and exercisable	4,303,588
Intrinsic value, vested and expected to vest	$ 6,253,298
Weighted average remaining contract term, outstanding	8 years 8 months 12 days	8 years 10 months 24 days
Weighted average remaining contractual term, exercisable	7 years 7 months 6 days
Weighted average remaining contractual term, vested and expected to vest	8 years 8 months 12 days

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Units (Details) - Restricted Stock Units - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Shares
Beginning balance (in shares)	491	11,301
Released (in shares)	(491)	(10,810)
Ending balance (in shares)	0	491
Weighted Average Grant Date Fair Value Per Share
Beginning weighted average grant date fair value (in dollars per share)	$ 0	$ 147.60
Released (in dollars per share)	147.60	9.37
Ending weighted average grant date fair value (in dollars per share)	$ 147.60	$ 15.38
Intrinsic value, outstanding	$ 0	$ 7,641	$ 14,013

Derivative Financial Instrume_3

Derivative Financial Instruments - Warrants (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Changes in the Company's derivative financial instruments liability balance
Balance of warrants outstanding at the beginning of the period (in shares) | shares	5,260,992	10,589,482
Balance of warrants outstanding at the end of the period (in shares) | shares	4,490,159	5,260,992
Balance of derivative financial instruments liability at the beginning of the period	$ 285
Change in fair value of derivative financial instruments—warrants during the year recognized as a loss in the statement of operations	(285)	$ 281
Balance of derivative financial instruments liability at the end of the period	$ 0	$ 285
Warrants to purchase Common Stock
Range of assumptions used to determine the fair value of warrants
Estimated fair value of Trovagene common stock (in dollars per share) | $ / shares	$ 6.01	$ 17.99
Warrants to purchase Common Stock | Black Scholes Option Pricing Method
Changes in the Company's derivative financial instruments liability balance
Balance of warrants outstanding at the beginning of the period (in shares) | shares	64,496	64,496
Balance of warrants outstanding at the end of the period (in shares) | shares	64,496	64,496
Balance of derivative financial instruments liability at the beginning of the period	$ 285	$ 4
Change in fair value of derivative financial instruments—warrants during the year recognized as a loss in the statement of operations	(285)	281
Balance of derivative financial instruments liability at the end of the period	$ 0	$ 285
Expected term | Warrants to purchase Common Stock
Range of assumptions used to determine the fair value of warrants
Expected warrant term	1 year 1 month 6 days	2 years 1 month 6 days
Risk-free interest rate | Warrants to purchase Common Stock
Range of assumptions used to determine the fair value of warrants
Measurement input	0.0041	0.0013
Expected volatility | Warrants to purchase Common Stock
Range of assumptions used to determine the fair value of warrants
Measurement input	0.83	1.16
Dividend yield | Warrants to purchase Common Stock
Range of assumptions used to determine the fair value of warrants
Measurement input	0	0

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Total available for sale investments	$ 128,878
Liabilities:
Derivative financial instruments—warrants	0	$ 285
Recurring basis
Assets:
Total included in cash and cash equivalents	10,990
Total available for sale investments	128,878
Total assets measured at fair value on a recurring basis	139,868	129,988
Liabilities:
Derivative financial instruments—warrants		285
Total liabilities measured at fair value on a recurring basis		285
Recurring basis | Certificate of deposit
Assets:
Total available for sale investments	1,260
Recurring basis | Corporate debt securities
Assets:
Total available for sale investments	88,390
Recurring basis | Commercial paper
Assets:
Total available for sale investments	14,454
Recurring basis | Non U.S. government
Assets:
Total available for sale investments	728
Recurring basis | U.S. treasury securities
Assets:
Total available for sale investments	24,046
Recurring basis | Money market fund
Assets:
Total included in cash and cash equivalents	10,990	129,988
Recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1)
Assets:
Total included in cash and cash equivalents	10,990
Total available for sale investments	24,046
Total assets measured at fair value on a recurring basis	35,036	129,988
Liabilities:
Derivative financial instruments—warrants		0
Total liabilities measured at fair value on a recurring basis		0
Recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Certificate of deposit
Assets:
Total available for sale investments	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Corporate debt securities
Assets:
Total available for sale investments	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Commercial paper
Assets:
Total available for sale investments	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Non U.S. government
Assets:
Total available for sale investments	0
Recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | U.S. treasury securities
Assets:
Total available for sale investments	24,046
Recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Money market fund
Assets:
Total included in cash and cash equivalents	10,990	129,988
Recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Total included in cash and cash equivalents	0
Total available for sale investments	104,832
Total assets measured at fair value on a recurring basis	104,832	0
Liabilities:
Derivative financial instruments—warrants		0
Total liabilities measured at fair value on a recurring basis		0
Recurring basis | Significant Other Observable Inputs (Level 2) | Certificate of deposit
Assets:
Total available for sale investments	1,260
Recurring basis | Significant Other Observable Inputs (Level 2) | Corporate debt securities
Assets:
Total available for sale investments	88,390
Recurring basis | Significant Other Observable Inputs (Level 2) | Commercial paper
Assets:
Total available for sale investments	14,454
Recurring basis | Significant Other Observable Inputs (Level 2) | Non U.S. government
Assets:
Total available for sale investments	728
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. treasury securities
Assets:
Total available for sale investments	0
Recurring basis | Significant Other Observable Inputs (Level 2) | Money market fund
Assets:
Total included in cash and cash equivalents	0	0
Recurring basis | Significant Unobservable Inputs (Level 3)
Assets:
Total included in cash and cash equivalents	0
Total available for sale investments	0
Total assets measured at fair value on a recurring basis	0	0
Liabilities:
Derivative financial instruments—warrants		285
Total liabilities measured at fair value on a recurring basis		285
Recurring basis | Significant Unobservable Inputs (Level 3) | Certificate of deposit
Assets:
Total available for sale investments	0
Recurring basis | Significant Unobservable Inputs (Level 3) | Corporate debt securities
Assets:
Total available for sale investments	0
Recurring basis | Significant Unobservable Inputs (Level 3) | Commercial paper
Assets:
Total available for sale investments	0
Recurring basis | Significant Unobservable Inputs (Level 3) | Non U.S. government
Assets:
Total available for sale investments	0
Recurring basis | Significant Unobservable Inputs (Level 3) | U.S. treasury securities
Assets:
Total available for sale investments	0
Recurring basis | Significant Unobservable Inputs (Level 3) | Money market fund
Assets:
Total included in cash and cash equivalents	$ 0	$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details)	12 Months Ended
	Dec. 31, 2021USD ($)
Operating loss carryforwards (NOLs)
Interest and/or penalties incurred	$ 0
Federal
Operating loss carryforwards (NOLs)
NOLs, subject to expiration	128,900,000
NOLs, not subject to expiration	73,300,000
California Franchise Tax Board
Operating loss carryforwards (NOLs)
NOLs	75,600,000
R&D credits | Federal
Operating loss carryforwards (NOLs)
Tax credits	2,400,000
R&D credits | California Franchise Tax Board
Operating loss carryforwards (NOLs)
Tax credits	$ 2,000,000

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Current:
State	$ 1	$ 1
Total current provision	1	1
Deferred:
Federal	(5,551)	(4,043)
State	(531)	(92)
Total deferred (benefit) expense	(6,082)	(4,135)
Valuation allowance	6,081	4,134
Total income tax provision	$ 0	$ 0

Income Taxes - Significant Comp

Income Taxes - Significant Components of Company's Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax computed at the federal statutory rate	$ (5,941)	$ (4,054)
State tax, net of federal tax benefit	(233)	(122)
Permanent items	62	261
Stock based compensation	325	81
Tax credits	(366)	(300)
Other	72	0
Valuation allowance increase (decrease)	6,081	4,134
Provision for income taxes	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Tax computed at the federal statutory rate	21.00%	21.00%
State tax, net of federal tax benefit	1.00%	1.00%
Permanent items	0.00%	(1.00%)
Stock based compensation	(1.00%)	(1.00%)
Tax credits	1.00%	2.00%
Other	0.00%	0.00%
Valuation allowance increase (decrease)	(22.00%)	(22.00%)
Provision for income taxes	0.00%	0.00%

Income Taxes - Significant Co_2

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Tax loss carryforwards	$ 47,902	$ 42,331
Research and development credits and other tax credits	4,035	3,904
Stock-based compensation	962	684
Other	1,750	1,116
Total deferred tax assets	54,649	48,035
Deferred tax liabilities:
Operating lease right-of-use assets	(611)	(74)
Other	0	(6)
Total deferred tax liabilities	(611)	(80)
Net deferred tax assets before valuation allowance	54,038	47,955
Valuation allowance	(54,038)	(47,955)
Net deferred tax asset	$ 0	$ 0

Commitments and Contingencies -

Commitments and Contingencies - Research and Development and Clinical Trial Agreements (Details) $ in Millions	Dec. 31, 2021USD ($)
Norviano
Loss Contingencies [Line Items]
Licensing and distribution rights commitment	$ 1

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 02, 2020	May 14, 2020	May 11, 2020	Nov. 30, 2021	May 31, 2021	May 31, 2020	Dec. 31, 2021		Dec. 31, 2020
Related Party Transaction [Line Items]
Research and development expense							$ 17,400
Sale of stock, shares issued (in shares)	6,500,000	146,854	447,761	2,400,000	2,000,000
Offering price (in dollars per share)	$ 13.50	$ 1.43	$ 1.34
Net proceeds	$ 94,000						34,187	[1]	$ 112,300	[2]
Other Affiliates
Related Party Transaction [Line Items]
Research and development expense							$ 0		$ 1,100
Director
Related Party Transaction [Line Items]
Sale of stock, shares issued (in shares)						447,761
Offering price (in dollars per share)						$ 1.34
Net proceeds						$ 600
[1]	Net of expenses of $0.8 million.
[2]	Net of expenses of $7.5 million, and fair value of warrants issued as a transaction advisory fee as of the date of issuance of $0.4 million.

COVID-19 (Details)

COVID-19 (Details) - Paycheck Protection Program, CARES Act	Apr. 15, 2020USD ($)
Unusual or Infrequent Item, or Both [Line Items]
Notes payable	$ 305,000
Interest rate	0.98%

Subsequent Events (Details)

Subsequent Events (Details) - shares	Jan. 05, 2022	Dec. 31, 2020	Jun. 30, 2020
Subsequent Event [Line Items]
Conversion of stock, shares issued (in shares)			1,546,700
Series E Convertible Preferred Stock
Subsequent Event [Line Items]
Shares converted (in shares)		210,780
Subsequent Event
Subsequent Event [Line Items]
Conversion of stock, shares issued (in shares)	1,342,357
Subsequent Event | Series E Convertible Preferred Stock
Subsequent Event [Line Items]
Shares converted (in shares)	327,535