Phase 1 results for anti-CD46 antibody drug conjugate FG-3246 follow a run of four late-stage flops for Fibrogen last year. FibroGen had a run of bad luck in its phase 3 trials last year, but phase 1 data posted this week suggest its earlier-stage pipeline still has potential. William Blair analysts branded the results “encouraging” and said they “appear to offer numerically improved efficacy metrics relative to alternate novel hormone therapy.”
They also noted that Novartis’ radioligand therapy Pluvicto scored a PSA50 response of 58% and a PFS of 12 months in a phase 3 trial among a similar patient population, while a combination of Exelixis’ Cabometyx and Roche’s Tecentriq demonstrated PFS of 4.2 months in a separate phase 3 prostate cancer trial. “While we acknowledge that the FDA cautions drawing solid conclusions based on the point estimate of progression-free survival from single-arm studies (i.e. it should preferably be interpreted in the context of hazard ratios), we believe the heavily pretreated nature of the study population, coupled with enrolling an unselected population, warrants further investigation of FG-3246 in prostate cancer,” the analysts concluded in an April 4 note. In FibroGen’s postmarket release yesterday, Chief Medical Officer Deyaa Adib, M.D., pointed out that the 8.7 month PFS rate related to “heavily pre-treated patients who received biologically active doses of FG-3246 in the second line or later setting prior to chemotherapy.” “These phase 1 data provide evidence of a favorable safety profile and promising clinical activity as further evidenced by prostate-specific antigen reduction of ≥ 50% and shrinking of measurable disease,” Adib added. “We look forward to publishing the totality of the phase 1 data as we advance the program further in the clinic.”