FDA requires additional safety trials for Lilly's Foundayo after approval

The FDA's approval letter for Foundayo, Eli Lilly's oral weight-loss drug, obliges the company to run additional clinical trials on heart risk, liver injury, retained stomach contents and breast-milk exposure — areas the agency says cannot be resolved with nonclinical or observational data ^[1][3]. The letter covering NDA 220934 is dated April 1 and appeared on the FDA's website April 14 ^[1][2].

Foundayo (orforglipron) was cleared for adults who have obesity, or who have overweight plus at least one weight-related condition, for use with a reduced-calorie diet and more physical activity ^[1]. Regulators reviewed it under the Commissioner's National Priority Voucher program, which is meant to speed decisions on products the agency deems important to public health or national security ^[2][3]. The application went to no advisory committee; the letter says it raised no controversial issues that would have justified one ^[1].

The pivotal language in the letter: "only a clinical trial (rather than a nonclinical or observational study) will be sufficient to assess a signal of a serious risk of retained gastric contents and to identify an unexpected serious risk for major adverse cardiovascular events (MACE), drug-induced liver injury (DILI), and exposure to orforglipron during lactation" ^[1][3].

Specific work follows from that finding. Lilly must finish Achieve-4, which pits orforglipron against insulin glargine in people who have type 2 diabetes and obesity or overweight and face elevated cardiovascular risk, and hand over a clinical study report describing any major heart or liver safety events that occurred ^[2][3]. An ultrasound-based clinical pharmacology trial will gauge how pausing doses and lengthening fasting periods change what stays in the stomach, work intended to "inform potential recommendations to mitigate the serious risk of pulmonary aspiration" ^[1][2][3]. A milk-only lactation study will measure drug concentrations in breast milk with a validated assay ^[1][2][3].

Pediatric and long-term obligations also appear. The agency waived studies for children from birth to under 6 years and deferred them for ages 6 through 11 and 12 through 17 ^[1]. An ongoing 72-week adolescent trial must wrap up in March 2028, with its final report that December, and an 84-week trial in children aged 6 to under 12 has a final report due February 2032 ^[1]. A pediatric obesity registry is to run at least 10 years, ending in a final report in April 2039 ^[1]. Two pregnancy studies are required — one registry with a draft protocol due October 2026 and a final report in June 2038, another using a different design with a final report in September 2035 ^[1]. A medullary thyroid carcinoma case series of at least 15 years is scheduled to finish in August 2042 and report in August 2043 ^[1].

A Lilly spokesperson told Reuters that late-stage testing showed no indications of liver damage and said the post-approval requirements fit "the agency's standard approach to ongoing safety evaluation of newly approved medicines" ^[2]. The Department of Health and Human Services, the FDA's parent department, did not immediately respond to a Reuters question ^[2]. BMO Capital Markets analyst Evan Seigerman called the volume of studies notable but said he expected no "meaningful impact on the competitive positioning of Lilly's asset," describing the requirements as "a reflection of conservatism from (the) FDA" ^[2].

Foundayo went on sale the week before April 14, taking on Novo Nordisk's oral Wegovy, available since January ^[2][3]. Weight-loss figures differ by outlet and by how adherence is counted: Reuters reports an 11% average reduction over 72 weeks for Foundayo against roughly 14% for the Wegovy pill over 64 weeks, while FiercePharma reports 12.4% for Foundayo among patients who stayed on treatment and 16.6% for the Wegovy pill, noting that comparing across trials is unreliable ^[2][3]. Lilly has emphasized that Foundayo can be taken at any hour with no food or water restrictions, whereas the Wegovy pill is taken in the morning on an empty stomach with no more than 4 ounces of water ^[3].

Why it matters for patients

The letter does not withdraw Foundayo, restrict its label or narrow its approved use ^[1]. It is not a finding that the drug causes heart problems or liver damage; the FDA has not announced such a finding, and Lilly says its late-stage data showed none ^[2].

What it does mean is that several safety questions the agency regards as unsettled — cardiovascular events, liver injury, food left in the stomach, and transfer into breast milk — will be answered, if at all, through trials that stretch years into the future ^[1][3]. Retained stomach contents matter to patients facing surgery or sedation, because anesthesia planning involves fasting; the letter points toward possible future advice on dose timing and fasting length, but none exists yet ^[1][3]. Whether orforglipron passes into breast milk or affects pregnancy outcomes has not been established ^[1].

What happens next

Draft protocols for the pregnancy registry and the thyroid cancer case series are due October 2026, with final protocols in October 2027 and April 2027 respectively ^[1]. The adolescent study ends March 2028 and reports in December 2028 ^[1]. Later milestones include a September 2035 report for the second pregnancy study, a June 2038 report for the registry, and an August 2043 report for the thyroid series ^[1]. Timelines for the lactation study and the gastric-emptying trial have not been disclosed ^[1][3].