Summit shares descend as PD-1/VEGF asset misses early survival mark

Summit's Ivonescimab Misses Early PFS Mark in HARMONi-3 Trial

Summit Therapeutics' shares dropped significantly after its anti-PD-1/VEGF bispecific antibody, ivonescimab, failed to meet an early interim progression-free survival (PFS) statistical bar in the Phase 3 HARMONi-3 trial for squamous non-small cell lung cancer (NSCLC). This interim analysis was intended to provide an opportunity for earlier regulatory engagement. Despite the setback, an independent data board recommended the study continue as planned, with a final PFS readout still anticipated in the second half of this year.

• The Phase 3 HARMONi-3 trial, evaluating ivonescimab in first-line squamous NSCLC, underwent an early interim progression-free survival (PFS) analysis. The asset did not meet the statistical threshold required for an early regulatory filing, indicating a lack of sufficient efficacy at this stage to warrant accelerated engagement with authorities.
• Following the announcement of the missed interim analysis, Summit Therapeutics experienced a significant financial impact. The company's shares plummeted by nearly 26%, closing at $16.12 per share, reflecting investor disappointment and concerns about the drug's future prospects for early approval.
• Despite the interim setback, the independent data board recommended that the HARMONi-3 study continue as planned. Summit remains on track for a pre-planned final PFS readout in the second half of this year, with the trial using Merck's Keytruda as a control arm, positioning ivonescimab as a potential new cornerstone therapy.

HARMONi-3's Interim PFS Miss: A Setback for Ivonescimab

Recent clinical studies have provided important insights into the evolving treatment landscape for NSCLC across multiple therapeutic classes. These trials demonstrate continued innovation in targeted therapy combinations, immunotherapy approaches, and biomarker-driven treatment selection strategies.

Ivonescimab's PD-1/VEGF Bispecifics in a Crowded NSCLC Field

The competitive landscape for PD-1/VEGF bispecific antibodies in NSCLC remains relatively nascent, with ivonescimab representing the first-approved agent in this class. While approximately twenty bispecifics and trispecifics are currently in clinical development globally, most remain in early-phase trials with limited public disclosure of specific intervention models.

• Cadonilimab is the primary identified competitor, representing another bispecific antibody approved in China for solid tumors, though specific NSCLC trial designs and intervention models were not detailed in available literature

• Multiple undisclosed bispecific antibodies targeting PD-1/PD-L1 and VEGF pathways are progressing through worldwide phase 3 trials as of 2026, though specific drug names and intervention protocols remain proprietary or unpublished

• Seven FDA-approved bispecific antibodies for solid tumors exist (amivantamab, tarlatamab, tebentafusp, zanidatamab, and zenocutuzumab), but these target different mechanisms of action rather than the PD-1/VEGF combination approach

• Conventional dual-drug combinations of separate PD-1 inhibitors and anti-angiogenic agents serve as the current standard comparators, with established intervention models combining immune checkpoint inhibitors with VEGF pathway inhibitors in sequential or concurrent protocols

Navigating the Evolving NSCLC Landscape: Where Ivonescimab Fits

The Non-small cell lung cancer treatment landscape has undergone dramatic transformation over the past five years, marked by seven FDA approvals in 2025 alone that fundamentally reshaped therapeutic approaches through precision oncology. These approvals encompassed MET-directed and TROP-2 antibody-drug conjugates, expanded EGFR strategies addressing exon 20 insertion mutations, ROS1 inhibitors, and HER2 options including both tumor-agnostic and mutation-selected approaches. This evolution has been driven by the integration of comprehensive diagnostic platforms including next-generation sequencing, fluorescence in situ hybridization, and immunohistochemistry, enabling more precise patient selection and treatment optimization.

Immunotherapy has emerged as a cornerstone of NSCLC management, with immune checkpoint inhibitors revolutionizing treatment across disease stages. The proportion of first-line ICI-treated patients in the Netherlands increased dramatically from 1.1% to 54.9% between 2016-2020, effectively replacing chemotherapy-only regimens as standard first-line treatment. Notable advances include the KEYNOTE-189 and CheckMate 227 studies demonstrating long-term overall survival benefits of immunotherapy combinations independent of PD-L1 status, while the CheckMate 9LA study showed rapid disease control with limited-course chemotherapy plus immunotherapy doublets. In the perioperative setting, phase III studies IMpower 010 and CheckMate 816 reported significant survival benefits, with neoadjuvant atezolizumab strategies showing disease control rates of 74.2% and 24-month overall survival rates of 73.7% in stage III disease.

Targeted therapy has seen remarkable expansion with third-generation inhibitors demonstrating superior efficacy profiles and addressing resistance mechanisms. Lorlatinib showed meaningful improvements over first-generation ALK inhibitors with hazard ratios of 0.28 for overall progression-free survival and 0.09 for CNS progression-free survival compared to crizotinib. The ADAURA study established postoperative osimertinib as standard care for EGFR-mutated early-stage disease, while FLAURA2 and MARIPOSA trials demonstrated that first-line combination strategies significantly prolong survival compared to monotherapy, particularly benefiting high-risk subgroups with brain metastases, L858R mutations, or TP53 co-mutations. Emerging therapeutic targets now include RET, NTRK fusions, c-MET alterations, KRAS, BRAF, and HER2 mutations, with novel approaches such as antibody-drug conjugates showing initial central nervous system efficacy and activity across multiple genomic alterations.

Ivonescimab's Squamous NSCLC Journey: Interim Hurdles, Enduring Promise

Ivonescimab, a novel bispecific antibody targeting both PD-1 and VEGF, has been heralded as a significant advancement in cancer immunotherapy, particularly for non-small cell lung cancer (NSCLC). Its innovative dual-targeting mechanism is designed to not only unleash anti-tumor immunity but also to modulate the tumor microenvironment by inhibiting angiogenesis, a strategy that has shown promising efficacy signals across various solid tumors. Indeed, the drug has already secured its first approval in China for EGFR-mutated locally advanced or metastatic non-squamous NSCLC patients who have progressed after TKI therapy, a testament to its potential in difficult-to-treat populations.

Further bolstering its profile, ivonescimab demonstrated superior progression-free survival (PFS) compared to pembrolizumab in first-line PD-L1-positive advanced NSCLC in the HARMONi-2 study, suggesting a potential paradigm shift in this common setting. Moreover, in the HARMONi-6 trial, ivonescimab combined with chemotherapy significantly improved PFS over tislelizumab plus chemotherapy in first-line advanced squamous NSCLC, regardless of PD-L1 status. These successes underscore the drug's broad applicability and the strength of its bispecific approach.

However, the recent news regarding an interim analysis of a separate Phase 3 HARMONi-3 trial for squamous NSCLC, where ivonescimab failed to meet an early statistical bar for PFS, introduces a nuanced challenge. While the independent data board recommended the study continue, this interim miss signals that the path to market for this specific squamous NSCLC indication may be more complex than initially anticipated. It highlights the inherent variability in trial outcomes, even for a drug with a strong mechanistic rationale and prior positive data in similar patient groups.

This development will likely prompt a strategic recalibration, potentially shifting immediate focus towards the already successful indications while awaiting the final data from the ongoing squamous NSCLC trial. Risks remain, including the possibility that the final HARMONi-3 readout for squamous NSCLC may not achieve its primary endpoint, and the drug's safety profile, which has shown a higher incidence of Grade ≥3 treatment-related adverse events in some trials compared to comparators, will require careful management in a competitive market. Ultimately, ivonescimab's journey in NSCLC is far from over, with its unique mechanism and existing positive data continuing to position it as a significant contender, albeit with a more cautious outlook for certain challenging subsets.