Orforglipron is the active ingredient in Foundayo, a new once-daily weight loss pill developed by Eli Lilly. Unlike the weight loss injections many people are already familiar with, Foundayo comes in tablet form and can be taken at any time of day without food or water restrictions. It received approval from the US Food and Drug Administration (FDA) on 1 April 2026, making it one of the most significant developments in obesity medicine in recent years.
Key facts at a glance:
- Foundayo is a once-daily oral GLP-1 receptor agonist
- FDA approved on 1 April 2026 for adults with obesity or overweight with weight-related health conditions
- Clinical trials showed up to 12.4% average body weight loss over 72 weeks at the highest dose
- Foundayo (orforglipron) was approved by the MHRA on 10 August 2026 and is licensed for use in the UK as a weight management treatment for eligible adults
- It cannot be taken alongside other GLP-1 medications such as Mounjaro or Wegovy
This article covers what orforglipron is, how it works, what the clinical trial evidence shows, its side effects, and what UK patients need to know about its current status.
What is Foundayo (orforglipron)?
Foundayo is the brand name for orforglipron, a small-molecule, non-peptide GLP-1 (glucagon-like peptide-1) receptor agonist. It was originally discovered by Chugai Pharmaceutical and licensed by Eli Lilly in 2018. It is now the second oral GLP-1 medication approved by the FDA for weight loss, following the approval of oral semaglutide (Wegovy pill) in December 2025.
How it differs from injectable GLP-1 treatments
Most GLP-1 medications currently available, including Mounjaro (tirzepatide) and Wegovy (semaglutide), are injectable treatments taken once weekly. Orforglipron is taken as a daily tablet, which is a meaningful practical difference for people who are needle-averse or who find weekly injections inconvenient.
What makes orforglipron particularly notable is that it's a small molecule rather than a peptide. Peptide-based GLP-1 drugs (like semaglutide) need to be injected because they'd be broken down in the stomach before reaching the bloodstream. Because orforglipron has a different molecular structure, it survives the digestive process and can be absorbed orally. This also means it doesn't require fasting or specific water intake before dosing, unlike some other oral formulations.
How orforglipron works
Like other GLP-1 receptor agonists, orforglipron works by mimicking the GLP-1 hormone that the body naturally releases after eating. This leads to:
- Reduced appetite and feelings of fullness after smaller meals
- Slower gastric emptying (food moves more slowly through the stomach)
- Improved regulation of blood sugar levels
- Reduced calorie intake over time
The result is a sustained reduction in body weight when combined with a reduced-calorie diet and increased physical activity, which is the basis for its approved use.
How effective is orforglipron? What the clinical trials show
The FDA approval of Foundayo was supported by two large, randomised, double-blind, placebo-controlled Phase 3 trials conducted under the ATTAIN programme. These trials enrolled adults with obesity, or overweight with at least one weight-related health condition, and ran for 72 weeks.
Phase 2 results (NEJM, 2023)
The first major efficacy data for orforglipron was published in the New England Journal of Medicine in September 2023. The Phase 2 trial enrolled 272 participants and tested four doses (12 mg, 24 mg, 36 mg, and 45 mg) against placebo.
Key findings at 36 weeks:
| Dose | Mean weight loss | ≥10% weight loss achieved |
|---|---|---|
| 12 mg | 9.4% | 46% of participants |
| 24 mg | 12.5% | 62% of participants |
| 36 mg | 14.7% | 75% of participants |
| 45 mg | 13.8% | 69% of participants |
| Placebo | 2.3% | 9% of participants |
Waist circumference also fell significantly across all doses, ranging from 9.6 cm to 13.6 cm compared to 4 cm with placebo.
Phase 3 ATTAIN-1 results (NEJM, 2025)
The Phase 3 ATTAIN-1 trial was published in the New England Journal of Medicine in September 2025 and presented at the European Association for the Study of Diabetes General Assembly. It enrolled over 3,000 adults and ran for 72 weeks.
Results at 72 weeks showed the following mean weight reductions compared to 2.1% with placebo:
- 6 mg dose: 7.5% weight loss
- 12 mg dose: 8.4% weight loss
- 36 mg dose: 11.2% weight loss
At the highest approved dose in the ATTAIN programme, 55% of participants lost at least 10% of their body weight, 36% lost at least 15%, and 19% lost at least 20%.
Cardiometabolic improvements, including reductions in waist circumference, systolic blood pressure, non-HDL cholesterol, and triglycerides, were also significant across all doses.
What this means in practice: The average weight loss with orforglipron is somewhat lower than that seen with injectable tirzepatide (Mounjaro) or injectable semaglutide (Wegovy), which can achieve 15-20%+ weight loss in trials. However, the cardiometabolic improvements seen with orforglipron were described by trial authors as comparable to those seen with injectable semaglutide, despite the modestly lower weight loss.
Dosing: how is Foundayo taken?
Foundayo is taken once daily as an oral tablet. There are no food or water restrictions, meaning it can be taken at any time of day, with or without a meal. This is a practical advantage over some other oral formulations that require fasting before dosing.
The FDA-approved dosing schedule follows a gradual escalation to help reduce gastrointestinal side effects:
| Weeks | Daily dose |
|---|---|
| Weeks 1–4 | 0.8 mg |
| Weeks 5–8 | 2.5 mg |
| Weeks 9–12 | 5.5 mg |
| Weeks 13–16 | 9 mg |
| Weeks 17–20 | 14.5 mg |
| Week 21 onwards | 17.2 mg (maximum dose) |
The maintenance dose is the highest tolerated dose reached during titration, up to a maximum of 17.2 mg once daily. Not everyone needs to reach the highest dose — some patients settle at a lower maintenance dose and stay there.
Important: Foundayo should not be taken alongside other GLP-1 receptor agonists, including Mounjaro (tirzepatide) or Wegovy (semaglutide). Using two GLP-1 medications at the same time increases the risk of side effects without providing additional benefit.
Side effects and safety
The safety profile of orforglipron is broadly consistent with other GLP-1 receptor agonists. The most common side effects are gastrointestinal in nature and tend to occur most frequently during the dose escalation phase, easing once the body adjusts.
Most common side effects
Based on pooled data from ATTAIN-1 and ATTAIN-2, involving 3,155 adults treated for up to 72 weeks, the following adverse reactions were reported in 5% or more of patients taking Foundayo and more frequently than with placebo:
| Side effect | Approximate frequency |
|---|---|
| Nausea | Very common (>10%) |
| Diarrhoea | Very common (>10%) |
| Vomiting | Common (5–10%) |
| Constipation | Common (5–10%) |
| Abdominal pain | Common (5–10%) |
| Decreased appetite | Common (5–10%) |
| Dyspepsia (indigestion) | Common (5–10%) |
| Fatigue | Common (5–10%) |
Most of these effects were mild to moderate in severity. They occurred primarily during dose escalation and resolved or reduced over time as patients settled on their maintenance dose. Discontinuation due to gastrointestinal events occurred in approximately 10% of patients taking the highest study dose, compared to 1.6% with placebo.
Boxed warning and serious risks
The FDA label for Foundayo includes a boxed warning regarding thyroid C-cell tumours. In animal studies, GLP-1 receptor agonists caused thyroid C-cell tumours at clinically relevant exposures. It is not yet known whether this risk applies to humans, but Foundayo is contraindicated in patients with:
- A personal or family history of medullary thyroid carcinoma (MTC)
- Multiple endocrine neoplasia syndrome type 2 (MEN 2)
Patients should report any symptoms of thyroid tumours, such as a lump in the neck, difficulty swallowing, or persistent hoarseness, to their prescriber promptly.
Who should not take Foundayo?
Foundayo is not suitable for everyone. It should not be used by patients who:
- Are pregnant or breastfeeding
- Have a history of pancreatitis (caution is advised)
- Are already taking another GLP-1 receptor agonist
- Have severe renal or hepatic impairment (specific guidance from a clinician is needed)
As with all prescription weight loss treatments, Foundayo should only be taken under the supervision of a qualified prescriber who can assess individual suitability.
Is orforglipron available in the UK?
Yes. Foundayo (orforglipron) was approved by the MHRA on 10 August 2026 and is licensed for use in the UK as a weight management treatment for eligible adults.
It was first approved in the United States by the FDA on 1 April 2026. That approval covered the US only. For a medicine to be prescribed here, it needed a separate marketing authorisation from the Medicines and Healthcare products Regulatory Agency (MHRA), which is exactly what has now been granted.
As a prescription-only medicine, orforglipron can only be supplied after a prescriber has reviewed your medical history and confirmed that the treatment is appropriate for you.
NHS availability is not guaranteed by MHRA approval alone. Both Mounjaro and Wegovy faced delays between regulatory approval and widespread NHS prescribing, and Foundayo remains subject to a separate NICE appraisal process before any NHS commissioning could follow. Here at Phlo Clinic, we offer clinically supervised weight loss programmes including Mounjaro and Wegovy, with ongoing support from our prescribing pharmacists, and we'll keep this page updated as private availability for Foundayo is confirmed.
How does orforglipron compare to Mounjaro and Wegovy?
It's natural to wonder how Foundayo stacks up against the injectable options currently available in the UK. The honest answer is that orforglipron sits in a different category rather than being a direct replacement, and the right choice depends on individual circumstances.
| Foundayo (orforglipron) | Mounjaro (tirzepatide) | Wegovy (semaglutide) | |
|---|---|---|---|
| Form | Daily oral tablet | Weekly injection | Weekly injection |
| Mechanism | GLP-1 agonist | GLP-1 + GIP dual agonist | GLP-1 agonist |
| Average weight loss (trials) | Up to 12.4% | Up to 20.9% | Up to 14.9% |
| UK availability | Approved (MHRA, Aug 2026) | Available | Available |
| No food restrictions | Yes | N/A | N/A |
| Needle-free | Yes | No | No |
A few things stand out from this comparison:
- Efficacy: The injectable options, particularly Mounjaro, produce greater average weight loss than orforglipron in clinical trials. Mounjaro's dual GIP and GLP-1 mechanism appears to deliver stronger results. That said, orforglipron's cardiometabolic improvements (blood pressure, cholesterol, triglycerides) were described by trial authors as comparable to those of injectable semaglutide.
- Convenience: For patients who are needle-averse or find weekly injections difficult to manage, an oral daily tablet is a meaningful practical advantage.
- Maintenance use: The ATTAIN-MAINTAIN trial data (May 2026) showed that patients who had already lost weight on injectable GLP-1 treatments could switch to orforglipron and maintain most of their weight loss. This positions Foundayo as a potential long-term maintenance option rather than a first-line treatment for maximum weight loss.
For a more detailed side-by-side breakdown of the injectable options currently available in the UK, see our Mounjaro vs Wegovy guide.
What else is orforglipron being studied for?
Weight management is only one part of Eli Lilly's development programme for orforglipron. The drug is being investigated across several other indications, which reflects the broader potential of GLP-1 receptor agonism beyond obesity treatment.
Current active research areas include:
- Type 2 diabetes: The ATTAIN-2 trial already demonstrated meaningful HbA1c reductions (up to 1.66%) alongside weight loss in adults with obesity and type 2 diabetes. A separate regulatory submission for the diabetes indication is expected.
- Obstructive sleep apnoea: GLP-1 medications have shown promise in reducing the severity of sleep apnoea
- Osteoarthritis knee pain: Weight loss reduces mechanical load on joints, and GLP-1 drugs may have additional anti-inflammatory effects that benefit joint pain independently of weight
- Hypertension: Reductions in systolic blood pressure were consistently observed across all ATTAIN doses, and a dedicated hypertension study is underway
- Peripheral artery disease and stress urinary incontinence: These are earlier-stage investigations but reflect the wide reach of GLP-1 biology
The breadth of this pipeline suggests orforglipron could become a platform treatment for multiple cardiometabolic and metabolic conditions, not just weight loss, over the coming years.
Summary
Foundayo (orforglipron) is a genuinely significant development in weight loss medicine. It's the first small-molecule, non-peptide oral GLP-1 receptor agonist to receive FDA approval for weight management, and its convenience as a no-restrictions daily tablet sets it apart from every injectable option currently on the market.
Key takeaway: Orforglipron produces meaningful weight loss (up to 12.4% at the highest approved dose over 72 weeks), with cardiometabolic benefits comparable to injectable semaglutide, and a safety profile consistent with the GLP-1 class. It's not as potent as tirzepatide (Mounjaro) for weight loss, but it's the most accessible delivery format yet for GLP-1 treatment.
Foundayo is now approved for use in the UK, alongside the treatments already available through services like Phlo Clinic, including Mounjaro and Wegovy, which remain clinically effective, well-established options for medically supervised weight loss.
The arrival of an oral GLP-1 option is an important signal for where the field is heading. For people who've been hesitant about injections, or who are looking for a longer-term maintenance option after achieving initial weight loss goals, orforglipron could be a meaningful addition to the options available.
If you'd like to explore your current options, you can browse our weight loss treatments or speak to one of our prescribing pharmacists.
References
- Eli Lilly and Company. FDA approves Lilly's Foundayo (orforglipron), the only GLP-1 pill for weight loss that can be taken any time of day without food or water restrictions. April 1, 2026. investor.lilly.com
- US Food and Drug Administration. FDA Approves First New Molecular Entity Under National Priority Voucher Program. April 1, 2026. fda.gov
- US Food and Drug Administration. Foundayo (orforglipron) Prescribing Information. April 2026. accessdata.fda.gov
- US Food and Drug Administration. Foundayo (orforglipron) Approval Letter. April 2026. accessdata.fda.gov
- Jastreboff AM, et al. Orforglipron for Obesity and Overweight in Adults without Diabetes. New England Journal of Medicine. September 2023. pubmed.ncbi.nlm.nih.gov
- American College of Cardiology. ATTAIN-1 Phase 3 Trial: Orforglipron for Weight Management. Journal Scan. September 2025. acc.org
- MedCentral. Orforglipron and Its Unique Delivery Method Expand Oral Obesity Treatment Options. Updated April 2, 2026. medcentral.com
- Consultant360. FDA Approves Orforglipron (Foundayo) for Chronic Weight Management. April 2026. consultant360.com
