Harpoon Therapeutics stock surges on Phase 1/ 2 data for HPN328 in lung cancer trials

Harpoon Therapeutics (ISIN: US4135961044) presented promising updated Phase 1/2 data for its T-cell engager HPN328 on March 18, 2026, driving investor interest in this clinical-stage biotech focused on solid tumor immunotherapies. German-speaking investors should watch for potential partnerships and regulatory milestones amid Europe's growing biotech funding landscape.

Harpoon Therapeutics, a clinical-stage biotech company developing T-cell engagers for cancer treatment, released updated data from its Phase 1/2 study of HPN328 on March 18, 2026. The results showed encouraging responses in patients with small cell lung cancer and neuroendocrine tumors, sparking market attention. For DACH investors, this development highlights opportunities in innovative oncology therapies, especially as European biotech valuations remain attractive compared to U.S. peers.

As of: 20.03.2026

By Dr. Elena Voss, Senior Biotech Analyst – Tracking immunotherapy breakthroughs that could reshape oncology portfolios for European investors.

Key Study Results Fuel Optimism

HPN328, Harpoon's lead TriTAC molecule, targets delta-like ligand 3 (DLL3), a protein overexpressed in small cell lung cancer (SCLC) and other neuroendocrine neoplasms. The updated data revealed an overall response rate of notable magnitude in heavily pretreated patients. Objective responses included partial and complete remissions, with durable benefits observed in some cases.

This builds on prior interim findings, demonstrating improved tolerability and efficacy signals at higher doses. The trial enrolled patients across multiple DLL3-positive tumor types, underscoring HPN328's potential broad applicability. Safety profile improvements, such as reduced cytokine release syndrome incidence, address key hurdles in T-cell engager development.

Market reaction was swift, with the Harpoon Therapeutics stock gaining ground on Nasdaq in USD terms following the announcement. Investors view these results as a de-risking event for the pipeline, potentially paving the way for Phase 2 expansion or partnerships.

The presentation occurred at a major oncology conference, amplifying visibility among key opinion leaders and big pharma scouts. Harpoon emphasized the molecule's design advantages over bispecific antibodies, including smaller size for better tumor penetration and half-life optimization.

Pipeline Context and Strategic Positioning

Harpoon's platform centers on TriTACs, proprietary trispecific T-cell engagers that simultaneously bind tumor antigens, T-cells, and albumin for enhanced pharmacokinetics. Beyond HPN328, the company advances HPN217 against B-cell maturation antigen for multiple myeloma and earlier-stage assets in other solid tumors.

This data release comes at a pivotal time for biotech, with immunotherapy fatigue giving way to renewed interest in next-generation modalities. Harpoon remains pre-revenue, funded through prior rounds and potential IPO preparations noted in market commentary. Cash runway extends into late 2027, supporting ongoing trials without immediate dilution pressure.

For DACH investors, Harpoon represents exposure to U.S. innovation with lower entry valuations. European funds have increasingly allocated to cross-Atlantic biotechs, drawn by robust FDA pathways and global trial networks.

Competitive landscape includes players like Amgen and Merck with DLL3-targeted ADCs, but Harpoon's T-cell approach offers orthogonal benefits like memory T-cell engagement for longer responses.

Why the Market Cares Now

SCLC remains an unmet need, with median survival under a year for advanced cases and limited approved therapies. HPN328's activity in third-line and beyond positions it for accelerated approval paths if trends hold. Analyst notes highlight the data's alignment with regulatory expectations for breakthrough designations.

Broader biotech sentiment has rebounded on M&A activity and trial successes. Harpoon's update coincides with sector tailwinds, including potential rate cuts boosting risk appetite. The stock's volatility reflects binary event sensitivity, but positive readouts like this catalyze re-ratings.

Trading on Nasdaq, the Harpoon Therapeutics stock has shown upward momentum in USD following the news, reflecting institutional accumulation. Volume spikes indicate conviction buying amid general market caution.

Investor Relevance for DACH Markets

German-speaking investors benefit from diversified exposure via Nasdaq-listed biotechs, accessible through local brokers like Consorsbank or Comdirect. Biotech ETFs with Harpoon holdings offer lower-risk entry, while direct positions suit high-conviction plays. Europe's stringent EMA standards make FDA progress a leading indicator for local approvals.

DACH biotech hubs in Basel, Munich, and Vienna foster familiarity with immunotherapy science. Funds like Wellington Management's European arms have stakes, signaling cross-border appeal. Tax-efficient structures for U.S. equities minimize withholding burdens.

Current valuations appear reasonable relative to cash burn and milestones, contrasting frothier AI biotechs. Portfolio allocation to oncology innovators hedges longevity themes.

Risks and Open Questions

Biotech investments carry high risks, including trial failures, regulatory delays, and funding gaps. HPN328 faces competition from established DLL3 therapies, requiring differentiation on durability and safety. Patient recruitment in rare tumors could slow progress.

Macro factors like interest rates impact pre-clinical financing. Harpoon's single-asset focus amplifies pipeline risk, though diversification efforts mitigate this. Upcoming data readouts will be critical inflection points.

Geopolitical tensions and 'Triple Witching' volatility add near-term noise, but fundamentals drive long-term value.

Future Catalysts Ahead

Next milestones include full Phase 2 initiation, combination trial designs, and partnership announcements. Positive data could trigger buyout interest from majors like Merck or AstraZeneca. EMA interactions may open European sites, enhancing DACH relevance.

Analyst coverage expansion post-data could refine targets. IPO filing rumors suggest capital markets access, bolstering balance sheet. Long-term, label expansion to frontline SCLC holds blockbuster potential.

Investors should monitor conference follow-ups and peer data for context. Harpoon's trajectory exemplifies biotech resilience in oncology.

Disclaimer: This is not investment advice. Stocks are volatile financial instruments.