Fibrogen’s pamrevlumab fails its first test

With the roxadustat opportunity restricted to ex-US markets, Fibrogen’s hopes of reinvigorating its share price rest on pamrevlumab. As such, failure of the antibody in its first test – non-ambulatory Duchenne muscular dystrophy in the Lelantos-1 trial – does not bode well. True, this was always a high-risk bet, with work here supported by anecdotal evidence and results from a small open-label trial, as Stifel analysts pointed out earlier this month. An antifibrosis mechanism is a unique approach in DMD – pamrevlumab targets connective tissue growth factor – though Fibrogen has a second shot here in Lelantos-2, in ambulatory DMD patients. That has a different primary endpoint versus Lelantos-1, which used performance of the upper limb 2.0 (PUL 2.0) score at week 52 compared with baseline; the only detail released today was that the study had not met that measure. Next up for the project is a much more important dataset, in idiopathic pulmonary fibrosis. Again, this is a readout not without risk, the successful phase 2 Praise trial notwithstanding. IPF is a space where mid-stage successes have frequently failed to be repeated in larger trials. Fibrogen shares opened 5% lower today. Much steeper falls should be expected if Zephyrus-1 disappoints.