Organization	6 Months Ended
Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Description of Business Harpoon Therapeutics, Inc. (the “Company”) is a clinical-stage immunotherapy company developing a novel class of T cell engagers that harness the power of the body’s immune system to treat patients suffering from cancer and other diseases. T cell engagers are engineered proteins that direct a patient’s own T cells to kill target cells that express specific proteins, or antigens, carried by the target cells. Using a proprietary Tri-specific T cell Activating Construct (“TriTAC”), platform, the Company is developing a pipeline of novel T cell engagers, or TriTACs, initially focused on the treatment of solid tumors and hematologic malignancies. The Company is also developing its ProTriTAC platform, which builds upon the core elements of the TriTAC platform by utilizing a prodrug approach designed to allow T cell engagers to address cancer targets that would otherwise be limited by on-target toxicities. The Company's third proprietary technology platform, extended release TriTAC-XR, is designed to mitigate cytokine release syndrome. The Company was incorporated in Delaware in March 2015 and is headquartered in South San Francisco, California. Follow-On Offering In January 2021, the Company sold an aggregate of 6,764,704 shares of its common stock for $107.6 million in net proceeds after deducting underwriting discounts and commissions and offering expenses. The offering was made pursuant to the Company’s shelf registration statement on Form S-3 (File No. 333-237175), declared effective by the SEC on April 23, 2020, a base prospectus dated April 23, 2020 and the related prospectus supplement dated January 6, 2021. Liquidity Since inception, the Company has incurred significant losses and has negative cash flows from operations. As of June 30, 2022, the Company had an accumulated deficit of $322.5 million. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development activities. As of June 30, 2022, the Company had cash, cash equivalents, and marketable securities of $90.2 million, which is available to fund future operations. The Company believes as of June 30, 2022 that its cash, cash equivalents and marketable securities provide sufficient capital resources to continue its operations for at least 12 months from the issuance date of the accompanying condensed financial statements. The Company will need to raise additional capital to support the completion of its research and development activities. The Company’s activities are subject to significant risks and uncertainties, including failing to secure additional funding to continue to operationalize the Company’s current technology and to advance the development of its product candidates.

Organization

6 Months Ended

Jun. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

1. Organization

Description of Business

Harpoon Therapeutics, Inc. (the “Company”) is a clinical-stage immunotherapy company developing a novel class of T cell engagers that harness the power of the body’s immune system to treat patients suffering from cancer and other diseases. T cell engagers are engineered proteins that direct a patient’s own T cells to kill target cells that express specific proteins, or antigens, carried by the target cells. Using a proprietary Tri-specific T cell Activating Construct (“TriTAC”), platform, the Company is developing a pipeline of novel T cell engagers, or TriTACs, initially focused on the treatment of solid tumors and hematologic malignancies. The Company is also developing its ProTriTAC platform, which builds upon the core elements of the TriTAC platform by utilizing a prodrug approach designed to allow T cell engagers to address cancer targets that would otherwise be limited by on-target toxicities. The Company's third proprietary technology platform, extended release TriTAC-XR, is designed to mitigate cytokine release syndrome. The Company was incorporated in Delaware in March 2015 and is headquartered in South San Francisco, California.

Follow-On Offering

In January 2021, the Company sold an aggregate of 6,764,704 shares of its common stock for $107.6 million in net proceeds after deducting underwriting discounts and commissions and offering expenses. The offering was made pursuant to the Company’s shelf registration statement on Form S-3 (File No. 333-237175), declared effective by the SEC on April 23, 2020, a base prospectus dated April 23, 2020 and the related prospectus supplement dated January 6, 2021.

Liquidity

Since inception, the Company has incurred significant losses and has negative cash flows from operations. As of June 30, 2022, the Company had an accumulated deficit of $322.5 million. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development activities.

As of June 30, 2022, the Company had cash, cash equivalents, and marketable securities of $90.2 million, which is available to fund future operations. The Company believes as of June 30, 2022 that its cash, cash equivalents and marketable securities provide sufficient capital resources to continue its operations for at least 12 months from the issuance date of the accompanying condensed financial statements. The Company will need to raise additional capital to support the completion of its research and development activities. The Company’s activities are subject to significant risks and uncertainties, including failing to secure additional funding to continue to operationalize the Company’s current technology and to advance the development of its product candidates.