Description of Business, Basis of Presentation, and Operating Segment	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Description of Business, Basis of Presentation, and Operating Segment	DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION, AND OPERATING SEGMENT (a) Description of Business Spectrum Pharmaceuticals, Inc. (“Spectrum”, the “Company”, “we”, “our”, or “us”) is a biopharmaceutical company, with a primary strategy comprised of acquiring, developing, and commercializing novel and targeted oncology therapies. Our in-house development organization includes clinical development, regulatory, quality and data management. We have two drugs in late-stage development: •Eflapegrastim, a novel long-acting granulocyte colony-stimulating factor (“G-CSF”) for the treatment of chemotherapy-induced neutropenia. On August 6, 2021, the Company announced the receipt of a complete response letter (“CRL”), that cited manufacturing deficiencies related both to the drug substance and drug product manufacturers. The Company believes it has completed the remediation of these deficiencies and resubmitted the Biologics License Application (“BLA”) on March 11, 2022; •Poziotinib, a novel irreversible tyrosine kinase inhibitor under investigation for non-small cell lung cancer (“NSCLC”) tumors with various mutations. On December 6, 2021, the Company announced it submitted its New Drug Application (“NDA”) for poziotinib to the FDA for use in patients with previously treated locally advanced or metastatic NSCLC with HER2 exon 20 insertion mutations. The NDA submission is based on the positive results of Cohort 2 from the ZENITH20 clinical trial, which assessed the safety and efficacy of poziotinib. The product has received Fast Track designation and there is currently no treatment specifically approved by the FDA for this indication. On February 11, 2022, the Company announced that it had received notice that the NDA had been accepted and received a PDUFA action date of November 24, 2022. (b) Basis of Presentation Principles of Consolidation The accompanying Consolidated Financial Statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and with the rules and regulations of the Securities and Exchange Commission (“SEC”). These financial statements include the financial position, results of operations, and cash flows of Spectrum and its subsidiaries, all of which are wholly-owned. All inter-company accounts and transactions among these legal entities have been eliminated in consolidation. Substantially all of the accumulated other comprehensive loss is comprised of foreign currency translation adjustments at December 31, 2021. Discontinued Operations - Sale of our Commercial Product Portfolio In March 2019, we completed the Commercial Product Portfolio Transaction (See Note 9 ). In accordance with applicable GAAP (ASC 205-20, Presentation of Financial Statements), the revenue-deriving activities and allocable expenses of our sold commercial operation, connected to the Commercial Product Portfolio, are separately classified as “discontinued” for all periods presented within the accompanying Consolidated Statements of Operations. Liquidity and Capital Resources We believe that our $100.6 million in aggregate cash, cash equivalents, and marketable securities as of December 31, 2021 combined with $20 million of equity financing received from Hanmi in January 2022 is sufficient to fund our current and planned operations for at least the next twelve months. We may, however, require additional liquidity as we continue to execute our business strategy, and in connection with opportunistic acquisitions or licensing arrangements. We anticipate that to the extent that we require additional liquidity, it will be funded through additional equity or debt financings, or out-licensing arrangements. However, we cannot provide assurance that we will be able to obtain this additional liquidity on terms favorable to us or our current stockholders, if at all. Additionally, our liquidity and our ability to fund our capital requirements are also dependent on our future financial performance which is subject to various market and economic factors that are beyond our control. (c) Operating Segment We operate one reportable operating segment that is focused exclusively on developing (and eventually marketing) oncology and hematology drug products. For the years ended December 31, 2021 and 2020, all of our operating costs and expenses were solely attributable to these activities (and as applicable, classified as “discontinued” within the accompanying Consolidated Statements of Operations).