Momenta Pharmaceuticals was presumably hoping to start its life as a pure-play, proprietary drug developer with something of a flourish, in the wake of its exit from biosimilars earlier this month. However, an R&D day last Thursday only served to underline the precarious nature of the company's very early pipeline, and the stock fell 13% to an eight-month low. A safety signal for the anti-FcRn antibody M281 was the biggest concern: phase I data unveiled creatine kinase elevations that caused three patients to discontinue treatment, while albumin reductions of around 25-35% were seen in a dose-escalation study. The anti-FcRn space is currently receiving much attention, and investors were not pleased to learn that Momenta’s contender might be differentiated by toxicities. These signals could turn out to be false, of course, but a significant wait for phase II proof-of-concept data means that shareholders will remain in the dark for some time. Planned trials are unlikely to read out before 2020. Momenta had already said it would need to raise money next year, and this disappointment-tinged R&D day will make this effort much harder.