Pfizer Inc. shares fell after it halted early development of an oral drug for weight loss on safety concerns, raising investor anxiety about an alternative therapy the company is still developing.

The drugmaker will stop work on lotiglipron based on data from phase 1 clinical trials and lab measurements showing elevated levels of enzymes called transaminases from an ongoing mid-stage study, according to a statement Monday. The enzymes play a key role in liver function. None of the patients reported liver side effects or symptoms, Pfizer said.

The shares fell as much as 5.6% at 10:51 a.m. in New York, their biggest intraday drop since February, 2022.

Struggling to recover from waning Covid vaccine demand, Pfizer is racing to catch up with Novo Nordisk A/S and Eli Lilly …