Pfizer Abandons Obesity Pill After Liver Injury Case, Viking Therapeutics Stock Surges

Pfizer has officially ended development of its experimental weight-loss pill, danuglipron, after a patient developed a potential drug-induced liver injury, marking the third major setback in the company’s obesity drug efforts. Though Pfizer claimed the liver issue resolved and enzyme levels across 1,400 patients were generally consistent with similar drugs, the company opted to halt the program following a full data review and input from regulators.

The development immediately turned investor attention to Viking Therapeutics, whose stock surged over 13% Monday. Viking’s own obesity drug candidate, VK2735, has shown promising weight-loss results with a favorable safety profile—making it a standout as competitors struggle with tolerability concerns. Analysts now see Viking not only as a frontrunner in the space but also as a possible takeover target, especially for companies like Pfizer now looking to reenter the race after high-profile failures.

While Pfizer will continue to test a different obesity drug, PF-07976016, which follows a new pathway by targeting the GIP receptor, the liver toxicity seen with danuglipron raises fresh questions about safety in the rapidly growing weight-loss market. With demand for effective and safe treatments surging, Viking’s cleaner safety data and upcoming Phase III trials could give it a key edge in a field still dominated by Eli Lilly and Novo Nordisk.