8-K: Immunome's Varegacestat Achieves Landmark Phase 3 Success

Immunome, Inc. announced positive topline results from its Phase 3 RINGSIDE trial for varegacestat in desmoid tumors, showing significant improvement in progression-free survival and objective response rates, with an NDA submission planned for Q2 2026.

Summary

• Immunome, Inc. reported positive topline data from the global pivotal Phase 3 RINGSIDE trial of varegacestat, an oral, once-daily gamma secretase inhibitor (GSI), for patients with progressing desmoid tumors.
• The trial met its primary endpoint, demonstrating an 84% reduction in the risk of disease progression or death (hazard ratio (HR) = 0.16, p<0.0001) compared to placebo.
• Varegacestat achieved a confirmed objective response rate (ORR) of 56% versus 9% for placebo (p<0.0001), as assessed by blinded independent central review.
• An exploratory analysis showed a median best change in tumor volume of -83% with varegacestat compared to +11% with placebo.
• All key secondary endpoints were met, including statistically significant improvements in landmark tumor volume reduction and worst pain intensity.
• Varegacestat was generally well tolerated with a manageable safety profile, consistent with the GSI class, though 55.6% of premenopausal women experienced ovarian toxicity.
• Immunome plans to submit a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) in Q2 2026.
• The company also provided an overview of its proprietary HC74 TOP1 inhibitor payload, designed to overcome limitations of existing TOP1 inhibitors by having lower efflux potential, higher permeability, and superior cytotoxicity.
• Preclinical studies for HC74 demonstrated superior properties compared to deruxtecan (DXd) and DXd ADCs, showing activity in models refractory to other TOP1i agents and superior bystander activity in target heterogeneous tumors.
• Immunome's pipeline includes IM-1021 (ROR1 ADC in dose escalation), IM-3050 (FAP-targeted radiotherapy entering Phase 1 early 2026), and several preclinical ADC candidates (IM-1617, IM-1340, IM-1335) with IND submissions anticipated in 2026.

Sentiment

Score: 9

Explanation: The filing reports highly positive Phase 3 clinical trial results for varegacestat, meeting all primary and key secondary endpoints with statistically significant and clinically meaningful improvements. The objective response rate is noted as the highest observed in this patient population. The safety profile is manageable, and an NDA submission is planned. Additionally, the company highlights a promising proprietary payload (HC74) with superior preclinical data and a robust pipeline, indicating strong future potential. These factors collectively point to a very positive outlook for the company's clinical and strategic advancements.

Positives

• Varegacestat achieved an 84% reduction in the risk of disease progression or death (HR = 0.16, p<0.0001) in the Phase 3 RINGSIDE trial, meeting its primary endpoint.
• The objective response rate (ORR) for varegacestat was 56% compared to 9% for placebo (p<0.0001), representing the highest ORR observed in a randomized clinical trial for desmoid tumors.
• Varegacestat demonstrated a median best change in tumor volume of -83% versus +11% with placebo.
• All key secondary endpoints, including landmark tumor volume reduction and worst pain intensity, were met with statistically significant improvements.
• Varegacestat exhibited a generally well-tolerated and manageable safety profile, consistent with the GSI class.
• The proprietary HC74 TOP1 inhibitor payload is designed to overcome payload resistance and increase bystander activity, showing superior cytotoxicity across 89 cell lines compared to DXd in preclinical studies.
• HC74 ADCs demonstrated activity in tumor models refractory to existing TOP1i therapies like T-DXd and irinotecan.
• Immunome has a robust pipeline with IM-1021 (ROR1 ADC) showing objective responses in B-cell lymphoma patients and IM-3050 (FAP Radiotherapy) initiating Phase 1 in early 2026.

Negatives

• The most common adverse events for varegacestat included diarrhea (82%), fatigue (44%), rash (43%), nausea (35%), and cough (34%).
• Approximately 55.6% of premenopausal women in the varegacestat treatment arm experienced ovarian toxicity.

Risks

• The RINGSIDE topline results are based on a preliminary analysis of key efficacy and safety data, which may change following a more comprehensive review.
• The NDA submission for varegacestat may be delayed based on regulatory feedback or other factors.
• Regulatory approvals for programs and product candidates may not be obtained, may be delayed, or may be subject to unanticipated conditions.
• The results of trials for varegacestat may not be deemed sufficient by the FDA to serve as the basis for an NDA submission or regulatory approval.
• There are risks associated with the potential safety and other complications from varegacestat.
• The labeling for varegacestat, if approved, may be restrictive.
• Uncertainties exist regarding the scope, progress, and expansion of developing and commercializing varegacestat, if approved.
• The size and growth of the market for varegacestat and the rate and degree of its market acceptance are uncertain.
• Preclinical studies are not always predictive of clinical data.
• Immunome may not be able to realize the benefits of its strategic transactions.
• Uncertainties are related to Immunome's capital requirements and expected cash runway.
• Immunome's ability to grow and advance its pipeline and successfully execute on its business plan faces risks.

Future Outlook

Immunome plans to submit a New Drug Application for varegacestat to the U.S. Food and Drug Administration in Q2 2026. The company will share additional data from the RINGSIDE trial at an upcoming major medical conference. Immunome anticipates multiple IND submissions in 2026 for its ADC pipeline, including IM-1617, IM-1340, and IM-1335, and expects to initiate Phase 1 for IM-3050 in early 2026 and report initial lymphoma data for IM-1021 in 2026. The company believes varegacestat has the potential to be a best-in-class option and become the standard of care for desmoid tumors, and that its HC74 ADCs have the potential for greater frequency and duration of benefit compared with existing TOP1 inhibitor payloads.

Management Comments

• Clay Siegall, Ph.D., CEO of Immunome, stated that the RINGSIDE topline results represent the highest objective response rate observed in a randomized clinical trial in this patient population, demonstrating varegacestat's potential to offer best-in-class results in a convenient, once-daily, oral medicine.
• Dr. Siegall also added that the RINGSIDE results are a major milestone for Immunome as the company advances its emerging pipeline of targeted oncology therapies with exceptional potential.
• Mrinal M. Gounder, M.D., sarcoma medical oncologist and RINGSIDE primary investigator, commented that the progression-free survival benefit, high response rate, and reduction in tumor volume with varegacestat are striking, elevating the role of GSIs and confirming varegacestat could become standard of care in desmoid tumors.

Industry Context

The positive Phase 3 results for varegacestat position it as a potential best-in-class oral, once-daily treatment for desmoid tumors, a rare and debilitating condition with limited approved systemic therapy options. The high objective response rate and significant progression-free survival benefit could establish varegacestat as a new standard of care, potentially displacing or complementing existing treatments. Immunome's focus on its proprietary HC74 TOP1 inhibitor payload addresses known limitations of current antibody-drug conjugates (ADCs), such as efflux resistance and limited bystander activity, suggesting a strategic move to differentiate its pipeline in the competitive oncology space. The development of IM-1021 (ROR1 ADC) and IM-3050 (FAP-targeted radiotherapy) further diversifies Immunome's portfolio, targeting novel mechanisms and expanding its presence in targeted oncology, aligning with broader industry trends towards precision medicine and overcoming resistance mechanisms.

Comparison to Industry Standards

• Varegacestat's 56% objective response rate (ORR) in the RINGSIDE trial is presented as the highest observed in a randomized clinical trial for desmoid tumors, significantly outperforming the 9% ORR of placebo.
• In comparison to other Phase 3 studies in desmoid tumors, varegacestat's 56% ORR is higher than Sorafenib (400mg once daily oral) which had an ORR of 33% (NCT02066181; N=87) and Nirogacestat (150 mg twice-daily oral) which had an ORR of 42% (DeFi; n=142).
• Varegacestat demonstrated a 78% longer half-life than Nirogacestat, suggesting a differentiated pharmacokinetic profile.
• Immunome's HC74 TOP1 inhibitor payload is designed to overcome limitations of existing TOP1 inhibitors like deruxtecan (DXd), which suffer from high efflux potential and low permeability.
• Preclinical studies showed HC74 had superior cytotoxic activity across 89 cell lines compared with DXd, and a lower efflux potential (efflux ratio of 10 for HC74 vs. 79 for DXd in Caco-2 permeability assay).
• HC74 demonstrated increased permeability (Papp of 9.01 x 10-6 cm/s for HC74 vs. 1.96 x 10-6 cm/s for DXd in MDCK II permeability assay), leading to superior bystander effect compared to DXd.
• HC74 ADCs showed activity in a colorectal cancer cell line (HCT-15) that was refractory to T-DXd or irinotecan, indicating potential to address resistance mechanisms that limit the clinical efficacy of existing TOP1i ADCs, such as high P-gp expression correlating with lower ORR and PFS in HER2-positive colorectal cancer patients treated with T-DXd.

Related Party Transactions

• Dr. Gounder, a sarcoma medical oncologist and RINGSIDE primary investigator, has financial interests related to Immunome.

Stakeholder Impact

• Shareholders: Highly positive clinical trial results for varegacestat are likely to increase investor confidence and potentially lead to a significant increase in share price, given the successful Phase 3 outcome and planned NDA submission.
• Patients with Desmoid Tumors: Varegacestat's strong efficacy and manageable safety profile offer a promising new oral, once-daily treatment option that could become a new standard of care, potentially improving quality of life and reducing disease progression.
• Healthcare Providers: The positive data and potential for a new best-in-class treatment will provide physicians with an additional, effective tool for managing desmoid tumors.
• Employees: The successful trial and pipeline advancements strengthen the company's position, potentially leading to growth opportunities and job security.
• Regulatory Authorities: The planned NDA submission will initiate the review process for potential market approval, requiring thorough evaluation of the submitted data.

Next Steps

• Submit a New Drug Application (NDA) for varegacestat to the U.S. Food and Drug Administration (FDA) in Q2 2026.
• Share additional data from the RINGSIDE trial at an upcoming major medical conference.
• Initiate Phase 1 for IM-3050 FAP-targeted radiotherapy in early 2026.
• Submit INDs for IM-1617 (First-in-Class Solid Tumor ADC) in early 2026.
• Submit INDs for IM-1340 (First-in-Class Solid Tumor ADC) in mid-2026.
• Submit INDs for IM-1335 (First-in-Class Solid Tumor ADC) in late 2026.
• Report initial lymphoma data for IM-1021 ROR1 ADC in 2026.

Key Dates

Recommendation

The filing presents exceptionally strong Phase 3 clinical trial results for varegacestat in desmoid tumors, meeting all primary and key secondary endpoints with statistically significant and clinically meaningful improvements. The 84% reduction in disease progression risk and 56% objective response rate are highly compelling, positioning varegacestat as a potential best-in-class therapy and new standard of care. The planned NDA submission in Q2 2026 indicates a clear path to market. Furthermore, the company's proprietary HC74 payload technology shows superior preclinical data, and a robust pipeline with multiple INDs and clinical milestones anticipated in 2026 suggests strong future growth potential. While acknowledging the preliminary nature of topline data and regulatory risks, the overwhelming positive clinical efficacy and strategic pipeline advancements make Immunome a highly attractive investment.

Keywords

Immunome, varegacestat, desmoid tumors, Phase 3 RINGSIDE, progression-free survival, objective response rate, gamma secretase inhibitor, GSI, NDA submission, HC74, TOP1 inhibitor, ADC, oncology, biotechnology, clinical trial, cancer therapy, ROR1 ADC, FAP radiotherapy