Harpoon Therapeutics : Corporate Presentation – August 2022

Spearheading Immunotherapies

INVESTOR PRESENTATION

AUGUST 2022

Forward-looking Statements

This presentation and accompanying oral commentary contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as "may," "will," "expect," "plan," "anticipate," "target," "estimate" and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. These forward looking statements are based on Harpoon's expectations and assumptions as of the date of this presentation. Each of these forward-looking statements involves risks and uncertainties that could cause Harpoon's clinical development programs, future results or performance to differ significantly from those expressed or implied by the forward-looking statements. Forward-looking statements contained in this presentation and accompanying oral commentary include, but are not limited to, statements about the progress, timing, scope, design and anticipated results of clinical trials, the timing of the presentation of data, the association of data with potential treatment outcomes, the development and advancement of platforms and product candidates, and the timing of development milestones for platforms and product candidates and future business, strategy and financial performance. Many factors may cause differences between current expectations and actual results, including unexpected safety or efficacy data observed during clinical studies, clinical trial site activation or enrollment rates that are lower than expected, unanticipated or greater than anticipated impacts or delays due to the COVID-19 pandemic, changes in expected or existing competition, changes in the regulatory environment, the uncertainties and timing of the regulatory approval process, the risk that initial or interim results from a clinical trial may not be predictive of the final results of the trial or the results of future trials, the risk that trials may be delayed and may not have satisfactory outcomes, and unexpected litigation or other disputes that impede clinical trial progress. Other factors that may cause Harpoon's actual results to differ from those expressed or implied in the forward-looking statements in this presentation and accompanying oral commentary are discussed in Harpoon's filings with the U.S. Securities and Exchange Commission, including the "Risk Factors" sections contained therein. Except as required by law, Harpoon assumes no obligation to update any forward- looking statements contained herein to reflect any change in expectations, even as new information becomes available.

Certain information contained in this presentation and statements made orally during this presentation relate to or are based on studies, publications, surveys and other data obtained from third-party sources and Harpoon's own internal estimates and research. While Harpoon believes these third-party studies, publications, surveys and other data to be reliable as of the date of this presentation, it has not independently verified, and make no representations as to the adequacy, fairness, accuracy or completeness of, any information obtained from third-party sources. In addition, no independent source has evaluated the reasonableness or accuracy of Harpoon's internal estimates or research and no reliance should be made on any information or statements made in this presentation relating to or based on such internal estimates and research.

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Clinical-StageImmuno-Oncology Company Advancing a Novel Portfolio of T Cell Engagers

Redirecting T Cells to Become Cancer Killers

Broad Pipeline in Immuno-Oncology

• 3 clinical-stage TriTACs across 6+ indications
• • Programs directed against clinically validated targets
  • Platform properties clinically validated

Novel T Cell Engaging

Platforms

• 3 technologies allowing for "off- the-shelf" T cell therapies
• Each designed with a distinct approach and profile
• • TriTAC® (Tri-specificT cell activating construct)

Strong

Capabilities

• Deep expertise in oncology, T cell engagement, and protein engineering
• Well-positionedfinancially
  ‐ $90.2M in cash & equivalents1

• ‐ Evidence of clinical benefit

• Advancing lead ProTriTAC™ candidate targeting EpCAM (IND-enabling)

• ProTriTAC (Prodrug activation in tumor micro-environment)
• TriTAC-XR (Extended-release with slow activation in circulation)

• Strong patent protection across platforms and programs

(1) As of 6/30/22

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Broad Pipeline of Immuno-Oncology Programs

Three Clinical Stage TriTAC Programs, Three Distinct TCE Platforms

Program	Indications	Stage of Development
	Preclinical	Phase 1	Phase 2	Phase 3
HPN328	Small Cell Lung Cancer &
(DLL3)	Other Tumors
HPN2171	Multiple Myeloma
(BCMA)
HPN536	Ovarian, Pancreatic & Other
(MSLN)	Solid Tumors
HPN601	Multiple Solid Tumors
(EpCAM)

Discovery

TriTACOncology

ProTriTAC Oncology

TriTAC-XROncology/

Non-Oncology

TriTAC ProTriTAC TriTAC-XR

(1) AbbVie retains option to worldwide exclusive rights

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HPN328

TriTAC Targeting DLL3