CT-388 for Weight Loss: Results, Side Effects, and Current Status

CT-388, also called enicepatide, is an investigational once-weekly injectable GLP-1/GIP receptor agonist being developed by Roche and Genentech for obesity, type 2 diabetes, and related metabolic conditions. Early clinical results are promising, but CT-388 is not approved and should not be used outside a regulated clinical trial.

In a Phase 2 obesity trial, Roche reported 22.5% placebo-adjusted weight loss at 48 weeks at the highest tested dose of 24 mg, without a reported weight-loss plateau. The main side effects reported so far are gastrointestinal and broadly consistent with the incretin drug class.

This article focuses on CT-388 for weight loss and current clinical development, not Roche’s separate oral GLP-1 candidate CT-996.

Who this is for: Readers tracking CT-388 trial results, side effects, dosing studied in research, and how close it may be to approval.

Who this is not for: Anyone trying to buy, compound, dose, or use CT-388 outside a regulated clinical trial.

Reviewed by VerifiedSupps Editorial Team • Last reviewed: May 18, 2026

Does CT-388 work for weight loss?

Early clinical data suggest CT-388 can produce substantial weight loss, but the evidence is not final. The strongest publicly available result so far is Roche’s 48-week Phase 2 obesity trial.

CT-388 is a dual GLP-1/GIP receptor agonist. That places it in the same broad drug class as tirzepatide, but CT-388 is a separate molecule with its own clinical development program, dosing research, and safety questions.

The practical meaning is simple: CT-388 is designed to influence appetite and metabolic signaling, not to “burn fat” directly. Weight loss with this type of drug is mainly expected through reduced energy intake, appetite control, and related metabolic effects.

For broader incretin-drug context, see our guides on retatrutide vs tirzepatide and how retatrutide works. Retatrutide uses a different triple-agonist strategy, while CT-388 is a dual GLP-1/GIP agonist.

How much weight did people lose on CT-388?

In Roche’s Phase 2 CT388-103 obesity trial, the highest tested CT-388 dose produced 22.5% placebo-adjusted weight loss at 48 weeks using the efficacy estimand. Roche also reported 18.3% placebo-adjusted weight loss using the treatment-regimen estimand.

That wording matters. “Placebo-adjusted” means the number reflects the difference between CT-388 and placebo, not necessarily the raw average weight loss from baseline. Different estimands also answer slightly different trial questions, especially around treatment adherence and discontinuation.

Responder data were also notable in the 24 mg group at week 48. Roche reported that 95.7% of participants achieved at least 5% weight loss, 87% achieved at least 10%, 47.8% achieved at least 20%, and 26.1% achieved at least 30%.

Roche also reported that 54% of participants on the 24 mg dose achieved a BMI below 30 kg/m2, compared with 13% in the placebo group. Among participants who had prediabetes at baseline, 73% on CT-388 24 mg achieved normal blood glucose levels at week 48, compared with 7.5% in the placebo group.

These are strong Phase 2 signals, but they are still not the same as completed Phase 3 evidence. For another example of why early obesity-drug results need careful interpretation, see our articles on MariTide for weight loss, mazdutide for weight loss, and survodutide for weight loss.

What CT-388 dose was used in studies?

CT-388 has no approved dose. In clinical studies, it has been tested as a once-weekly subcutaneous injection with gradual dose escalation.

The Phase 2 CT388-103 trial evaluated low, middle, and high doses across five dosing cohorts, with 24 mg as the highest tested dose. The study used different up-titration schemes rather than starting participants immediately at the highest dose.

• Route: Subcutaneous injection.
• Frequency: Once weekly in clinical trials.
• Highest tested Phase 2 dose: 24 mg.
• Dose escalation: Used in research to improve tolerability and evaluate different regimens.
• Consumer dose: None. There is no approved dosing schedule for CT-388.

This is a critical safety point. Trial doses should not be copied from press releases, registry entries, or online forums. A dose used in a monitored clinical trial is not a safe do-it-yourself protocol.

If you are seeing CT-388 sold online as a “research peptide,” read our guide on whether peptides are safe. Unapproved peptide products can raise concerns around identity, sterility, dosing accuracy, contaminants, storage, and lack of medical monitoring.

What are the side effects of CT-388?

The most common CT-388 side effects reported so far are gastrointestinal. Roche described the Phase 2 safety profile as generally consistent with the incretin class, with no new or unexpected safety signals in the topline release.

In the Phase 2 obesity trial, Roche reported that most gastrointestinal adverse events were mild to moderate. Discontinuation due to adverse events was 5.9% across CT-388 arms compared with 1.3% in the placebo arm.

• Likely GI effects: Nausea, vomiting, diarrhea, constipation, abdominal discomfort, and reduced appetite may occur with GLP-1/GIP drugs.
• Injection-related effects: Bruising, discomfort, swelling, itching, or other local injection-site reactions are possible with subcutaneous injections.
• Discontinuation: The reported Phase 2 adverse-event discontinuation rate was relatively low, but full safety tables are still needed.
• Long-term unknowns: Larger studies are needed to better assess gallbladder events, pancreatitis signals, kidney complications, dehydration risk, and rare adverse events.
• Lean mass: Large weight loss can include lean mass loss if protein intake, resistance training, and clinical monitoring are not managed well.

The current safety picture is encouraging but incomplete. Topline trial summaries are useful, but they do not replace full published safety tables, longer follow-up, and regulatory review.

The lean-mass question matters for all strong weight-loss drugs. For more context, see our guide on retatrutide and muscle loss and our article on how much protein you actually need.

Who should avoid CT-388?

Outside a regulated clinical trial, everyone should avoid CT-388. It is not approved, does not have a final prescribing label, and has not completed the evidence package needed for routine medical use.

If CT-388 is eventually approved, the final label will determine contraindications, warnings, monitoring needs, and eligible populations. Until then, caution is especially important for groups that commonly require careful screening with incretin-based therapies.

• People who are pregnant, trying to become pregnant, or breastfeeding.
• People with a history of pancreatitis, gallbladder disease, or severe gastrointestinal motility problems.
• People using insulin, sulfonylureas, or other glucose-lowering medications where appetite and glucose changes could affect hypoglycemia risk.
• People with kidney disease or a history of dehydration from vomiting or diarrhea.
• People with active eating disorders or a high risk of under-eating.
• Anyone considering gray-market injections, research vials, or compounded products labeled as CT-388.

A basic rule applies: promising trial data do not make an investigational drug safe to self-administer. CT-388 belongs in clinical research until regulators review the full data.

What is the current status of CT-388?

As of May 18, 2026, CT-388 is not approved for weight loss or type 2 diabetes. Roche’s latest public pipeline materials list enicepatide, the name used for CT-388, as a Phase 3 obesity asset.

Roche has initiated Phase 3 ENITH trials for obesity with and without type 2 diabetes. CT-388 is also being studied in an additional Phase 2 trial in people with obesity or overweight and type 2 diabetes.

No reliable approval date can be given yet. Phase 3 trials must complete, results must be analyzed, and regulators must review efficacy, safety, dosing, labeling, and manufacturing before CT-388 could be used commercially.

How does CT-388 compare with tirzepatide and other weight-loss drugs?

CT-388 is promising, but it should not be called better than tirzepatide or other approved obesity medications yet. The drugs have not been compared head-to-head in a completed obesity trial, and CT-388 has not completed Phase 3 development.

The cleanest comparison is by development stage. Tirzepatide is approved and has large Phase 3 data. CT-388 is investigational with strong Phase 2 data. Other pipeline drugs use different mechanisms and should not be ranked from headline numbers alone.

• CT-388 vs tirzepatide is the most direct comparison because both are GLP-1/GIP drugs.
• Retatrutide trial results matter because retatrutide uses a GLP-1/GIP/glucagon triple-agonist strategy.
• CagriSema for weight loss combines semaglutide with an amylin analog approach.
• Cagrilintide, petrelintide, and amycretin are examples of amylin-pathway obesity research.
• Pemvidutide is being studied for weight loss and fatty liver with a different receptor strategy.

The practical takeaway: CT-388 is one to watch, not one to use. Phase 3 results will determine whether its strong Phase 2 signal becomes a clinically useful, regulator-reviewed treatment option.