On May 21, 2026 Obsidian Therapeutics, Inc., a clinical-stage biopharmaceutical company harnessing novel protein-regulation technology to develop engineered tumor-infiltrating lymphocyte (TIL) cell therapies, reported positive Phase 2 results in patients with advanced melanoma from the Phase 1/2 Agni-01 multicenter study of OBX-115. These data will be presented in an oral presentation by Allison S. Betof, M.D., Ph.D., FASCO, associate professor of medicine (oncology), Stanford School of Medicine, on Monday, June 1, 2026, at the 2026 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting in Chicago, IL.
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OBX-115 is a novel engineered TIL cell therapy armored with pharmacologically regulatable membrane-bound IL15 and designed to deliver an improved, patient-centric treatment regimen. With its potentially reduced treatment burden driven by option for less-invasive core needle biopsy tumor tissue procurement, exclusively low-dose lymphodepletion (LD) compatible with outpatient administration and elimination of IL2 in the treatment regimen, OBX-115, if approved, has the potential to become a meaningful therapeutic option and expand the cell therapy eligible population of patients with advanced or metastatic melanoma.
Oral Presentation Title: OBX-115 engineered tumor-infiltrating lymphocyte (TIL) cell therapy with regulatable membrane-bound IL15 (mbIL15) in patients with advanced melanoma that has progressed on/after immune checkpoint inhibitors (ICI): Phase 2 results
Session Title: Oral Abstract Session – Melanoma/Skin Cancers
Abstract: #9507
Location: Grand Ballroom S100bc
Session Date and Time: June 1, 8:00AM-11:00AM CT
Presentation Time: 10:12 AM-10:24 AM CT
Data to be presented are from the single-arm open-label Phase 1/2 Agni-01 multicenter study (NCT06060613) assessing the safety and efficacy of OBX-115 in adult patients with advanced melanoma that has progressed following treatment with ICI. Results from the January 22, 2026 data cutoff include 15 patients treated at the recommended phase 2 dose (RP2D), with n=6 from Phase 1 and n=9 from Phase 2.
OBX-115 demonstrated strong efficacy with a 67% objective response rate (ORR) in a difficult-to-treat advanced melanoma patient population
Study conducted in high unmet need melanoma patients, including a majority (93%) who were previously treated with doublet ICI
73% of patients had progression after anti–PD-1 + anti–CTLA-4 doublet therapy, a group with particularly low response rates to subsequent therapy
67% ORR (per RECIST v1.1), including 2 confirmed complete responses (CR) and 8 confirmed partial responses (PR) (compared to 1 CR and 9 PRs in abstract text)
Durable clinical benefit, including 8 of 10 responses ongoing as of the median 4.3 month study follow-up
OBX-115 continues to deliver consistent, favorable safety profile; treatment regimen with low-dose lymphodepletion and no IL2
All patients received low-dose LD, including 4 in the outpatient setting
No dose-limiting toxicities (DLT), treatment-related mortality (TRM), immune effector cell-associated neurotoxicity syndrome (ICANS) or ICU transfers
Majority of treatment-emergent adverse effects (TEAEs) occurring in ≥20% of patients were Grade 2 or less
Dr. Betof commented, "These data highlight OBX-115’s promising safety and efficacy profile, demonstrating the potential for durable benefit with low rates of major safety signals, including no DLTs, ICU transfer or TRM. The notable reduction in patient treatment burden relative to other therapies, driven by attributes such as core needle biopsy tumor tissue procurement and treatment regimen with outpatient-compatible low-dose lymphodepletion and without IL2, could be very beneficial and broaden the number of cell therapy eligible patients."
"Results from the Agni-01 study, including the 67% ORR, with 80% of responses ongoing as of the median 4.3 month study follow up, further emphasize OBX-115’s potential in advanced melanoma. We are highly encouraged by the anticipated benefit demonstrated in patients with difficult-to-treat advanced melanoma, including patients with disease progression following anti–PD-1 combination exposure," said Parameswaran Hari, M.D., M.S., Chief Medical Officer of Obsidian. "We have been in discussions with the FDA, and after reaching alignment on key design elements including eligibility criteria, clinical trial endpoints and drug product potency assay, plan to pursue a single-arm accelerated approval pathway. We look forward to continuing to advance OBX-115 through the clinic and plan to begin treating patients in the registration-enabling cohort of our multicenter study in mid-2026."
Obsidian is also investigating OBX-115 in patients with non-small cell lung cancer (NSCLC) in the Agni-01 trial. NSCLC Phase 1 data are expected in the first half of 2027.
About OBX-115
Obsidian’s lead investigational cytoTIL15 program, OBX-115, is a novel engineered tumor-derived autologous T cell immunotherapy (tumor-infiltrating lymphocyte [TIL] cell therapy) armored with pharmacologically regulatable membrane-bound IL15 (mbIL15). OBX-115 has the potential, if approved, to become a meaningful therapeutic option for patients with advanced or metastatic melanoma and other solid tumors by leveraging the expected benefits of mbIL15 and Obsidian’s proprietary, differentiated manufacturing process designed to enhance persistence, antitumor activity, and clinical safety of TIL cell therapy. Obsidian is investigating OBX-115 in the phase 1/2 Agni-01 multicenter trial in patients with advanced solid tumors (NCT06060613).
(Press release, Obsidian Therapeutics, MAY 21, 2026, View Source [SID1234665975])