Kyntra Bio Announces Positive Phase 1b/2 Data For FG-3246 Combined With Enzalutamide In Metastatic Castration-Resistant Prostate Cancer, To Be Presented At ASCO GU 2026

Kyntra Bio, formerly known as FibroGen, announced that data on the anti-tumor activity of FG-3246 in combination with enzalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC) from an investigator-sponsored Phase 1b/2 study will be presented at the 2026 American Society of Clinical Oncology Genitourinary Cancers Symposium (ASCO GU), scheduled for February 26-28, 2026, in San Francisco, California.

The study, led by Principal Investigator Dr. Rahul Aggarwal, Professor of Medicine at the University of California, San Francisco, has demonstrated encouraging preliminary anti-tumor activity of FG-3246 in combination with enzalutamide. In particular, patients who had progressed on only one prior androgen receptor pathway inhibitor (ARPI) achieved a median radiographic progression-free survival (rPFS) of 10.1 months, highlighting the potential of FG-3246 in earlier lines of therapy. Dr. Aggarwal also noted that early observations suggest a positive trend between tumor uptake of FG-3180, a CD46-targeting PET imaging agent, and PSA50 response, suggesting the biomarker could be useful in guiding patient selection for future studies.

Thane Wettig, Chief Executive Officer of Kyntra Bio, commented that the data expand on the clinically meaningful results previously observed with FG-3246. He emphasized that the rPFS achieved in patients progressing on only one prior ARPI, combined with the ability to mitigate neutropenia-related adverse events through prophylactic G-CSF use, supports the design of the ongoing Phase 2 monotherapy trial. Interim analysis from the Phase 2 study is expected in the second half of 2026, and the company aims to further evaluate the potential utility of FG-3180 as a predictive biomarker.

The Phase 1b/2 study included 44 biomarker-unselected patients with progressive mCRPC, including 17 participants in the Phase 1b dose-escalation portion. Eligible patients had progressed on at least one prior ARPI, while those previously treated with chemotherapy in the castration-resistant setting were excluded. More than 60% of enrolled patients had progressed on two or more prior ARPIs, including prior enzalutamide therapy. The primary endpoint of the dose-escalation phase was to assess dose-limiting toxicities and determine the maximum tolerated dose and recommended dose for Phase 2, established at 2.1 mg/kg of FG-3246 and 160 mg/day of enzalutamide. The primary endpoint of the Phase 2 expansion phase was the composite response rate, defined as a PSA50 response and/or objective response per RECIST v1.1 criteria. Secondary endpoints included PSA50 response rate, objective response rate, rPFS, overall survival, and treatment-related adverse events.

FG-3246 combined with enzalutamide demonstrated a composite response rate of 21% across the overall cohort, increasing to 40% among patients who had progressed on only one prior ARPI. Median rPFS was 7.0 months for the overall population and 10.1 months for patients with only one prior ARPI, consistent across different prior therapies. Higher tumor uptake of FG-3180 showed a trend toward a greater likelihood of PSA50 response, supporting its potential as a biomarker for patient selection.

The combination therapy was generally well tolerated, with a safety profile similar to that observed in the previous Phase 1 monotherapy trial of FG-3246. Neutropenia risk was effectively managed with prophylactic G-CSF, and the most common treatment-related adverse events included fatigue, peripheral neuropathy, anorexia, and dysgeusia. Some patients discontinued therapy due to cumulative toxicities, particularly peripheral neuropathy.

The poster presentation, titled “A Phase 1b/2 Study of FOR46 (FG-3246) in Combination with Enzalutamide (ENZA) in Patients with Metastatic Castration-Resistant Prostate Cancer (mCRPC),” is scheduled for February 26, 2026, from 11:30 AM to 12:45 PM PT. FG-3246 is currently being evaluated in a Phase 2 monotherapy trial, with interim data anticipated in the second half of 2026. This trial incorporates FG-3180, the CD46-directed PET imaging agent, to assess CD46 expression levels in lesions and further explore the correlation between biomarker status and response to FG-3246, as well as its potential utility for patient selection in future studies.