Glucagon-like peptide-1 (GLP-1) drugs that dominate the global obesity treatment market have run into a wave of lawsuits over vision loss. Patients in the U.S. have filed a string of claims saying they developed non-arteritic anterior ischemic optic neuropathy (NAION) after taking Ozempic, Wegovy or Zepbound. The new safety questions have not slowed development, however. Competition among drugmakers to capture the fast-growing market is intensifying, and the main battleground is shifting quickly from weekly injections to oral pills and long-acting shots given once a month or less often.
Lawsuits alleging a link between GLP-1 treatments and NAION are mounting against Novo Nordisk and Eli Lilly in the U.S., according to The Wall Street Journal and other outlets. U.S. law firm Weitz & Luxenberg has filed more than 90 suits in New Jersey state court since 2025 on behalf of patients who say they developed NAION after using Ozempic or Wegovy. Patients who say they lost their sight after using GLP-1 drugs from Novo and Lilly are also pursuing claims in federal court in Philadelphia.
NAION is a condition in which reduced blood flow to the optic nerve can cause sudden vision impairment or loss. Some studies have found a higher risk of NAION among GLP-1 users, but findings have been inconsistent across studies and a causal relationship has not been established. The U.S. Food and Drug Administration is investigating the potential link.
Drugmakers counter that no causal relationship between the drugs and vision loss has been proven. Novo Nordisk says an analysis of randomized controlled trial data for its GLP-1 treatments found no increase in NAION risk. Tina Vilsboll, Novo's chief medical officer, told the WSJ there was no signal that NAION should be a genuine concern and that no causal relationship was apparent. Eli Lilly says it continues to review ophthalmic data with patient safety as its top priority. In court filings, Lilly has argued that research to date cannot establish that GLP-1 drugs cause NAION and that its medicines are safe and effective.
Despite the safety questions, drugmakers find it hard to ease off the GLP-1 race because the market is expanding so quickly. Mounjaro, Lilly's GLP-1 diabetes treatment, posted global sales of $9.943 billion in the second quarter alone. First-half sales reached $18.605 billion, up 106% from a year earlier. Adding the $9.088 billion in first-half sales of Zepbound, which markets the same ingredient, tirzepatide, for obesity, the two products generated $27.693 billion in six months.
The market is set to grow further. According to global pharmaceutical market researcher IQVIA, the world obesity drug market is projected to expand nearly 40% in a single year, from $66 billion last year to $92 billion this year. IQVIA expects the market could reach $105 billion to $200 billion after 2027. By around 2030, the obesity drug market is expected to become more segmented by delivery method, dosing interval and tolerability, with long-acting treatments given once a month or less often entering the market in earnest. How conveniently patients can stay on treatment over the long term is emerging as a competitive factor alongside weight-loss efficacy.
The first front is oral treatments. Novo Nordisk and Eli Lilly each launched an oral obesity drug in the U.S. this year and are competing to seize an early lead. Lilly said this month that its oral obesity treatment Foundayo had captured more than 30% of patients newly starting an oral obesity drug in the U.S. Novo expects oral formulations to account for more than a third of GLP-1-based obesity treatment use by 2030. The appeal of oral drugs lies in drawing in patients averse to injections and expanding the market itself through relatively simple dosing.
Injectables are also shifting strategy, cutting the number of doses sharply rather than eliminating the needle. A leading candidate is Amgen's MariTide. Amgen is running Phase 3 trials of MariTide and is testing not only monthly dosing but also longer intervals. Trials are also under way to switch patients from weekly semaglutide or tirzepatide to MariTide given every eight weeks or once a quarter. The aim is to move beyond the weekly dosing that has become the market standard to treatments requiring an injection only once every two or three months.
Korean pharmaceutical and biotech companies are also rushing into the next-generation obesity drug race. Hanmi Pharmaceutical (128940.KS) is pursuing commercialization of the GLP-1 drug efpeglenatide while developing oral and patch versions as well as a monthly long-acting formulation to improve dosing convenience. It is also advancing clinical development of next-generation candidates including HM15275, a weekly triple agonist designed to boost weight loss while minimizing muscle loss, and HM17321, which aims to reduce fat while promoting muscle gain. Celltrion (068270.KS) is developing GLP-1-based multi-agonists and an oral treatment, while Daewoong Pharmaceutical (069620.KS) is working on a semaglutide-based microneedle patch and a long-acting injection.
Korean biotechs are even more active in developing long-acting formulations that stretch dosing intervals. Peptron (087010.KQ) is developing PT403, which applies its proprietary sustained-release platform SmartDepot to semaglutide to extend dosing from weekly to monthly, and filed an investigational new drug application for a Phase 1 trial with the Ministry of Food and Drug Safety last month. Inventage Lab (389470.KQ) is developing IVL3021, a monthly long-acting semaglutide formulation. G2Gbio (456160.KQ) is developing one-month and three-month formulations of semaglutide while also working on monthly versions of next-generation obesity drugs including CagriSema, tirzepatide and retatrutide.
The decisive battleground in the next-generation obesity drug market is widening from how much weight a drug can take off to how comfortably patients can stay on treatment. Oral drugs offer the convenience of avoiding injections, while long-acting treatments counter with the convenience of not having to take a pill every day. With GLP-1 drugs facing a new challenge in the form of safety questions, competition for a global obesity drug market set to top $100 billion is entering a second round beyond the weekly injection.
"As the weight-loss efficacy of GLP-1 obesity drugs has risen to a considerable level, safety, dosing convenience and treatment persistence will become important factors separating products going forward," an industry official said. "Formulation technologies that widen patient options, such as oral drugs and long-acting versions given once a month or less often, are likely to become the core axis of competition in the next-generation obesity drug market."
