Phenomix Sciences and Mayo Clinic Present New Research on Predicting GLP-1 Response and Weight Regain at ObesityWeek® 2026

Studies presented at ObesityWeek 2026, including two further validating the MyPhenome^® test, strengthen the evidence base for precision obesity medicine.

• Phenomix Sciences co-founder Andres Acosta, M.D., Ph.D., and his team at Mayo Clinic presented three new studies at ObesityWeek 2026 exploring how genetics and clinical characteristics may help explain why patients respond so differently to GLP-1 medications such as semaglutide and tirzepatide.
• A real-world study of more than 45,000 patients found that weight regain after stopping semaglutide or tirzepatide varies widely, from about two months to regain half of lost weight for the highest-risk patients to about 19 months for the lowest-risk, and introduced a model to help predict who is most at risk.
• Two additional studies found that Phenomix's MyPhenome^® genetic test, developed from Mayo Clinic research, helped identify patients more likely to respond to tirzepatide and semaglutide.

MENLO PARK, Calif., Nov. 12, 2026 /PRNewswire/ -- Phenomix Sciences (Phenomix), the first commercial precision obesity medicine biotechnology company, today announced new research presented at ObesityWeek^® 2026, reinforcing that obesity is a complex, chronic disease and that patients can respond very differently to the same treatment. Led by Mayo Clinic physician scientist and Phenomix co-founder Andres Acosta, M.D., Ph.D., the studies explore how genetics and clinical characteristics may help explain those differences and support more individualized obesity care.

In the largest of the studies, researchers developed a model to help predict which patients are most at risk of regaining weight after stopping GLP-1 medications. The study, "Predicting Weight Regain After GLP-1 Discontinuation: A Real-World Prognostic Model," followed 45,017 adults for up to 36 months after they stopped semaglutide (28,599 patients) or tirzepatide (16,418 patients). Researchers measured how long it took patients to regain at least half of the weight they had lost on treatment, then built separate prediction models for each medication.

Key findings include:

• Patients lost an average of 11.3% of their body weight on semaglutide and 11.0% on tirzepatide. During follow-up, they regained an average of 73.7% and 69.2% of that lost weight, respectively.
• On average, patients regained half of their lost weight six months after stopping semaglutide and nearly five months after stopping tirzepatide.
• Among patients in the held-out test group, those the model ranked highest risk regained half their lost weight in 1.8 months (semaglutide) and 2.0 months (tirzepatide), compared with 19.0 and 19.2 months for those ranked lowest risk (both p<0.001).
• Greater weight loss on treatment and longer treatment duration were the strongest factors associated with a longer time before regain. Patients who lost 20% or more of their body weight still maintained a net loss of 13% (semaglutide) and 16% (tirzepatide) two years after stopping.

"For too long, obesity care has treated every patient as if they have the same underlying disease," said Dr. Acosta. "The studies my team is presenting at ObesityWeek show that genetic markers and clinical characteristics can help us anticipate how a patient is likely to respond to a medication and how quickly they may regain weight if they stop. That's the kind of insight clinicians need to make precision medicine part of everyday obesity care."

In addition to the weight regain findings, additional studies presented at ObesityWeek add to the evidence that Phenomix's MyPhenome^® test, a simple cheek swab that determines the root biological factors that can cause obesity, can help identify which patients are most likely to achieve meaningful weight loss on GLP-1 medications.

The first, "Machine-Learning Assisted Gene Risk Score for Satiation Biomarker Predicts Tirzepatide Weight-Loss Response," evaluates the MyPhenome test in patients treated with tirzepatide. Among 3,378 patients, those with the Hungry Gut phenotype lost an average of 17.0% of their body weight at 12 months, compared with 13.9% for other patients (p<0.0001). The difference appeared as early as three months and grew over time. Hungry Gut patients were far less likely to see little or no response. Only 2.7% lost less than 5% of their body weight, compared with 19.1% of other patients.

The second, "Predicting Response to GLP-1 Therapies Using a Machine Learning Clinical Calculator," combined the MyPhenome results with clinical and demographic data to predict response to semaglutide before treatment begins. Among 3,094 patients, those the calculator placed in the high predicted response group lost an average of 18.3% of their body weight at 12 months, compared with 11.4% in the intermediate group and 6.5% in the low group. Genetics was the strongest contributor to the prediction, ahead of age, BMI, sex, and diabetes status.

"Weight regain is one of the most pressing questions in obesity care, and these findings show why getting the right treatment from the start matters," said Mark Bagnall, CEO of Phenomix Sciences. "The MyPhenome results show that clinicians have the ability to identify who is likely to respond before treatment starts, rather than after months of trial and error. As more patients start GLP-1 medications, that kind of insight can help clinicians and payers make better decisions about which treatment is right for each patient and for how long."

MyPhenome is in use by nearly 400 healthcare clinics nationwide and available direct to patients online. Phenomix recently partnered with Proto360 Health, a metabolic care platform founded by board-certified obesity medicine physicians, to integrate the MyPhenome test into Proto360's comprehensive metabolic care program.

For more information about Phenomix Sciences and supporting research, visit phenomixsciences.com.

About Phenomix Sciences
Phenomix Sciences is a precision obesity biotechnology company transforming obesity care by putting patients at the center of therapeutic innovation. Through proprietary genetic testing, advanced analytics, rich clinical data, and technology exclusively licensed from Mayo Clinic, Phenomix delivers individualized insights into how patients respond to specific weight loss interventions. These insights not only inform clinical decision-making for patients but also help pharmaceutical and medical device partners refine trials, identify high-responder populations, and accelerate the development of more targeted, effective therapies. By aligning patient biology with drug discovery, Phenomix is shaping a more personalized and impactful future for obesity treatment. Phenomix is backed by Health2047, the innovation arm of the American Medical Association, which helps startups transform bold ideas into solutions that change healthcare for the better. Learn more at www.phenomixsciences.com.

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