Amgen's MariTide Advances in Obesity Trials, Stock Falls 0.38% on 145th-Ranked Volume as Investors Weigh Competitive Hurdles

Market Snapshot

Amgen (AMGN) closed January 13, 2026, with a 0.38% decline, trimming its value by approximately $0.38 per share. Trading volume totaled $770 million, ranking the stock 145th in terms of daily trading activity. While the modest price drop suggests limited immediate market reaction, the volume indicates sustained investor interest in the biopharmaceutical giant as it navigates a pivotal phase in its obesity drug pipeline.

Key Drivers

The release of positive Phase 2 trial data for Amgen’s experimental obesity drug MariTide on January 13 underscored the company’s progress in addressing a growing market. The drug demonstrated its ability to maintain weight loss in patients over a two-year period, with a "large majority" of participants retaining results even when doses were reduced or administered quarterly. This aligns with Amgen’s strategic emphasis on less frequent dosing—a differentiator in a competitive landscape dominated by weekly injections like Eli Lilly’s Zepbound and Novo Nordisk’s Wegovy. CEO Bob Bradway highlighted these findings at the J.P. Morgan Healthcare Conference, emphasizing MariTide’s potential as a maintenance therapy and its improved tolerability in the second year of treatment, with significantly reduced gastrointestinal side effects compared to initial trials.

However, the muted stock response reflects lingering investor concerns. While MariTide’s weight-loss efficacy (up to 20% in non-diabetic patients and 17% in those with type 2 diabetes) is robust, skepticism persists over its ability to outpace rivals in speed and convenience. Analysts note that Amgen’s drug faces a high bar: it must not only match the efficacy of GLP-1/GIP combination therapies but also mitigate its historically high vomiting rates, which reached 40% in early trials. The company’s assertion that lower starting doses in future trials will reduce side effects remains unproven in large-scale Phase 3 studies, leaving some investors cautious.

The competitive landscape further complicates MariTide’s path. Novo Nordisk and Eli Lilly have established strong market positions with weekly GLP-1/GIP therapies, which are now standard in obesity and diabetes treatment. Amgen’s approach—activating GLP-1 receptors while blocking GIP receptors—offers a novel mechanism but faces the challenge of educating providers and patients. Jay Bradner, Amgen’s head of R&D, stressed the company’s leadership in developing less frequent dosing, but investors remain focused on real-world adoption rates and pricing power, which have yet to be tested.

Strategic initiatives beyond MariTide also influence Amgen’s valuation. The company’s recent $600 million investment in a new R&D center in California signals long-term commitment to innovation, while partnerships like its collaboration with telehealth provider Ro to address treatment barriers highlight efforts to expand access. However, these moves must offset the impending patent expirations of key drugs like Enbrel and Neulasta, which analysts project will drive revenue declines in the coming years. The success of MariTide is thus critical to maintaining Amgen’s growth trajectory and justifying its current valuation multiples.

In summary, while MariTide’s Phase 2 results validate Amgen’s scientific innovation, the stock’s muted performance reflects market pragmatism. Investors are weighing the drug’s potential to disrupt the obesity market against its unproven scalability, competitive pressures, and Amgen’s broader portfolio challenges. The upcoming Phase 3 trials and regulatory filings will be pivotal in determining whether MariTide can secure a leadership position in a rapidly evolving therapeutic space.