Mumbai, Aug. 24 -- There is a particular silence that follows a great run of luck. Dr Reddy's Laboratories Ltd (DRL) heard it in July, when it reported that first-quarter profit had fallen by nearly 70%, with North American sales-long the company's engine-down by more than a third. To read the headlines, you would think a champion had stumbled. To listen to G.V. Prasad, the Hyderabad drugmaker's co-chairman and managing director, is to understand that the music simply stopped.

The bad news came with a name attached: semaglutide. DRL had been racing to launch a generic of the molecule behind diabetes and weightloss drugs Ozempic and Wegovy, the most coveted franchise in medicine-in Canada. During scale-up, a batch of the active ingredient...