Quick answer: TERN-601 was an investigational, once-daily oral small-molecule GLP-1 receptor agonist developed by Terns Pharmaceuticals for obesity. It reached Phase 2 testing and produced statistically significant weight loss (up to 4.6% placebo-adjusted at 12 weeks), but Terns discontinued the program in October 2025 after three participants developed liver enzyme elevations during the Phase 2 trial, two of which were assessed as consistent with drug-induced liver injury (DILI). TERN-601 is not approved, is no longer in active development, and is documented here for historical and research reference.
Research Snapshot
| Peptide category | Not a peptide — small-molecule GLP-1 receptor agonist |
| Primary research interest | Obesity / weight management (formerly) |
| Highest available evidence | Published, peer-reviewed human Phase 1 and Phase 2 clinical trial data |
| Human research available | Yes — Phase 1 (28-day MAD) and Phase 2 (12-week, FALCON) completed and published |
| Development status | Discontinued — Terns Pharmaceuticals ended the program in October 2025 over liver safety findings |
| Regulatory status | Never approved; development discontinued before any regulatory filing |
| Last reviewed | 2026-09-27 |
Technical Identity
| Primary name | TERN-601 |
| Alternative names | None identified in a primary source reviewed for this page |
| Peptide sequence | Not applicable — TERN-601 is a small synthetic molecule, not a peptide |
| Amino-acid length | Not applicable |
| Molecular formula | Not publicly disclosed in a primary source reviewed for this page |
| Molecular weight | Not publicly disclosed in a primary source reviewed for this page |
| CAS Registry Number | Not publicly disclosed in a primary source reviewed for this page |
| PubChem CID | Not reliably established from a primary source reviewed for this page |
| UNII | Not publicly disclosed |
| DrugBank ID | Not publicly disclosed |
| Chemical modifications | Reported to share a core scaffold/pharmacophore with the discontinued oral GLP-1 candidates danuglipron and lotiglipron, but with lower solubility and higher plasma protein binding |
| Peptide class | Not applicable — small-molecule GLP-1 receptor agonist |
| Primary biological target | GLP-1 receptor (potent, selective agonist with minimal activity at closely related GPCRs) |
| Developer or originator | Terns Pharmaceuticals |
| Development status | Discontinued (October 2025) |
What Is TERN-601?
TERN-601 was an investigational, once-daily, oral, small-molecule GLP-1 receptor agonist developed by Terns Pharmaceuticals, a clinical-stage biopharmaceutical company. It was part of the same wave of “oral GLP-1” development programs as Eli Lilly’s orforglipron, Pfizer’s discontinued danuglipron, AstraZeneca’s elecoglipron, and other company-specific candidates such as RGT-075, all aiming to bring the GLP-1 receptor agonist mechanism — proven effective for weight loss by injectable drugs like semaglutide — into a convenient daily pill.
Published research describes TERN-601 as sharing a core chemical scaffold with two other discontinued oral GLP-1 candidates, Pfizer’s danuglipron and lotiglipron, though with different solubility and protein-binding properties. Notably, lotiglipron’s development was previously halted after liver enzyme elevations were observed in its trials — a pattern that would later recur with TERN-601 as well.
TERN-601 advanced from a Phase 1 multiple-ascending-dose (MAD) study, with positive topline results announced in September 2024, into a Phase 2 study (internally named FALCON) in adults with obesity or overweight. Terns reported statistically significant weight-loss results from the 12-week Phase 2 trial in October 2025. However, in that same announcement, the company disclosed that three trial participants had developed elevated liver enzymes during the post-treatment follow-up period, with findings in two participants assessed as consistent with drug-induced liver injury (DILI). Citing these liver safety findings, Terns Pharmaceuticals discontinued the TERN-601 program and said it would not advance the compound or invest further in its metabolic-disease portfolio, redirecting resources to an unrelated oncology asset (TERN-701).
How Does It Work?
Plain-English Explanation
Like other GLP-1 receptor agonists, TERN-601 was designed to activate the GLP-1 receptor in the brain and gut, reducing hunger, increasing the feeling of fullness after eating, and slowing how quickly the stomach empties. This combination reduces overall food intake and was expected to produce weight loss similar in kind, though more modest in degree, to injectable GLP-1 drugs.
Technical Explanation
Published pharmacology data describe TERN-601 as a potent, selective agonist of the human GLP-1 receptor with minimal activity against closely related G-protein-coupled receptors. Its terminal elimination half-life was reported at approximately 3 to 5 hours, notably short for a once-daily drug — but at doses above 100 mg, prolonged absorption extended target (receptor) coverage to roughly 16–24 hours, which is what allowed once-daily dosing despite the short plasma half-life. Delayed gastric emptying was observed pharmacodynamically across all active treatment groups in both Phase 1 and Phase 2 testing, consistent with on-target GLP-1 receptor activation.
Potential Benefits and Research Applications
Weight Loss in Obesity
TERN-601 has been shown, in a published, peer-reviewed, placebo-controlled Phase 2 trial, to produce statistically significant placebo-adjusted weight loss at doses of 500 mg and above over 12 weeks, with the largest effect (about 4.6% placebo-adjusted, roughly 5.0 kg) seen at the standard-titration 500 mg dose. This is human clinical-trial evidence at the strongest tier available for an investigational compound — but the program was subsequently discontinued for safety reasons before any longer trial could establish whether this weight loss would continue to increase, plateau, or how it would compare with more established oral or injectable options over months rather than weeks.
What Dosage Information Circulates?
Figures in this section summarize amounts and schedules reported in published research or circulating online. Their inclusion documents what is reported and does not establish that a regimen is verified, safe, effective, or appropriate. TERN-601 development has been discontinued — these figures are historical clinical-trial data, not an active or recommended regimen.
| Reported use or research objective | Route reported | Amount reported | Frequency reported | Reported duration | Evidence or source category |
|---|---|---|---|---|---|
| Phase 1, 28-day multiple-ascending-dose | Oral, fasting | 240 mg, 500 mg, or 740 mg once daily (maintenance); titrated from a 100 mg starting dose over 9–15 days | Once daily | 28 days | Published human clinical trial (peer-reviewed) |
| Phase 2 (FALCON), 12-week obesity trial | Oral, no food restriction | 250 mg, 500 mg (slow titration), 500 mg (standard titration), or 750 mg once daily; titrated from 100 mg over 3–9 weeks | Once daily | 12 weeks | Published human clinical trial (peer-reviewed) |
Explanation of the Reported Figures
Unlike most investigational compounds on this site, TERN-601’s dosage information comes from a full peer-reviewed publication (Garvey et al., published in the journal Obesity) rather than only company press releases — making it among the better-documented entries in this pipeline category, even though the drug itself was discontinued. The 500 mg once-daily dose (standard titration) produced the largest weight-loss effect in the Phase 2 trial and is the figure most emphasized in the topline results. The 750 mg dose, despite being the highest tested, produced less weight loss than 500 mg — an inverted dose-response relationship that is unusual for this drug class and was not fully explained in the sources reviewed for this page; it may reflect differences in tolerability-driven dose reductions or study-specific factors at the highest dose. No community, practitioner, or vendor-reported figures for TERN-601 were identified — like the other oral small-molecule candidates on this site, it never reached community or off-label research-chemical channels, remaining confined to company-sponsored trials throughout its development and discontinuation.
Detailed Dosage and Protocol Evidence
Amounts Studied in Human Research
| Research objective | Amount studied | Frequency | Duration | Route | Study population | Source |
|---|---|---|---|---|---|---|
| Phase 1, safety/PK/weight loss (MAD) | 240 mg (n=10), 500 mg (n=9), 740 mg (n=9), each vs. placebo | Once daily | 28 days | Oral, fasting | 37 adults, inpatient, 3:1 active:placebo randomization | Garvey et al., Obesity (2026); Terns Phase 1 topline press release |
| Phase 2 (FALCON), efficacy/safety | 250 mg (n=33), 500 mg slow-titration (n=34), 500 mg (n=34), 750 mg (n=33), vs. placebo (n=33) | Once daily | 12 weeks | Oral, no food restriction | 167 adults with obesity/overweight, 17 US centers, stratified by BMI and sex | Garvey et al., Obesity (2026); Terns Phase 2 topline press release |
Amounts Studied in Animal Research
Not consistently reported. No published animal dosing data for TERN-601 were identified in the sources reviewed for this page.
Practitioner and Community-Reported Protocols
Not consistently reported. TERN-601 was a proprietary, patent-protected compound confined to company-sponsored clinical trials and was discontinued before reaching the market; no practitioner-reported or community-reported protocols were identified.
Conflicts and Unanswered Questions
The reduced weight-loss effect at the highest 750 mg dose compared with 500 mg was not fully explained in the sources reviewed for this page. Whether the liver enzyme elevations observed post-treatment were dose-dependent, idiosyncratic, or related to a specific patient subgroup was not conclusively established before the program was discontinued — Terns’ announcement described the causality assessment for two of the three cases as “consistent with” rather than definitively confirming drug-induced liver injury, and one case was attributed to gallstones and considered unlikely to be drug-related. Because clinical development stopped after 12 weeks of exposure, no data exist on longer-term efficacy, weight-loss durability, or long-term safety.
Important Published Research
Garvey et al., “Oral GLP-1RA TERN-601 for Adults With Obesity/Overweight: Placebo-Controlled, Multiple-Ascending-Dose, Phase 1 and 2 Studies” (Obesity, 2026)
Study type: Combined publication of a Phase 1 (28-day, multiple-ascending-dose, inpatient) study and a Phase 2 (12-week, outpatient, FALCON) study, both randomized, double-blind, and placebo-controlled.
Subjects: Phase 1: 37 adults (3:1 TERN-601:placebo randomization). Phase 2: 167 adults with obesity or overweight across 17 US research centers, stratified by BMI and sex (134 TERN-601, 33 placebo).
Doses: Phase 1 — 240 mg, 500 mg, and 740 mg once daily. Phase 2 — 250 mg, 500 mg (slow titration), 500 mg (standard titration), and 750 mg once daily.
Findings: Weight loss was dose-related in Phase 1 (up to −4.9% placebo-adjusted at 740 mg by day 29) and showed its largest Phase 2 effect at the 500 mg standard-titration dose (−4.6% placebo-adjusted, about −5.0 kg, at week 12; statistically significant, p<0.0001), with 46.4% of participants on that dose achieving at least 5% weight loss versus 15.4% on placebo. Gastrointestinal adverse events (nausea, vomiting, constipation, diarrhea) were common and dose-related. Three participants developed elevated liver enzymes during post-treatment follow-up; two were assessed as consistent with drug-induced liver injury, with one confirmed by liver biopsy, and all cases resolved without specific treatment. The Phase 2 discontinuation rate due to adverse events was reported as approximately 11.9–24.6% depending on the source.
Limitations: The Phase 2 trial ran only 12 weeks — short relative to the 36-plus-week trials typically used to establish sustained weight-loss efficacy — and the trial was not designed or powered to definitively establish drug-induced liver injury causality in the small number of affected participants. Long-term safety and efficacy data do not exist because the program was discontinued.
In plain English: TERN-601 produced real, statistically meaningful weight loss in a properly controlled human trial, but a small number of participants developed concerning liver test abnormalities after stopping treatment, and the company judged the risk-benefit balance unfavorable enough to end the program entirely rather than pursue further studies to clarify the liver signal.
Timing, Duration, and Research Variables
TERN-601 was dosed once daily by mouth in every study identified. The Phase 1 titration schedule ran 9–15 days to reach maintenance dose, under fasting conditions and inpatient supervision. The Phase 2 titration schedule ran longer (3–9 weeks depending on target dose) and did not require fasting. Despite a short 3–5 hour plasma half-life, prolonged absorption at doses above 100 mg extended functional receptor coverage to roughly 16–24 hours, supporting once-daily dosing. The liver enzyme elevations that led to discontinuation were notably observed during the post-treatment follow-up period (starting around week 8 or later), not necessarily while participants were still on active treatment — a pattern that influenced how seriously the finding was taken.
Combinations and Related Research
No formally studied combination trials involving TERN-601 and another drug were identified. TERN-601 is mechanistically and structurally related to two other discontinued oral GLP-1 candidates, Pfizer’s danuglipron and lotiglipron — lotiglipron was itself discontinued years earlier after showing liver enzyme elevations in its own trials, a parallel that is mechanistically and historically relevant context for TERN-601’s own discontinuation. No practitioner-reported or community-reported combination protocols exist, as the compound never left controlled clinical trials.
Side Effects, Risks, and Limitations
Gastrointestinal side effects were common and dose-related across TERN-601’s trials: nausea was reported in roughly 48–88% of treated participants depending on dose and study, vomiting in roughly 6–78%, and constipation in roughly 6–56%, with diarrhea also reported in Phase 2. These were predominantly mild to moderate, with no severe GI adverse events reported, and are broadly consistent with the GLP-1 receptor agonist class as a whole.
The clinically decisive finding was hepatic, not gastrointestinal: three Phase 2 participants developed grade 3 liver enzyme elevations during post-treatment follow-up, with two cases in the 500 mg arm assessed as consistent with drug-induced liver injury (one confirmed by liver biopsy) and a third attributed to gallstones and considered unlikely to be drug-related. All cases were reported to have resolved without specific treatment, and no hepatotoxicity was observed in the earlier Phase 1 study. Citing this signal, Terns Pharmaceuticals discontinued TERN-601’s clinical development entirely in October 2025 rather than pursue further studies to characterize or rule out the liver risk. Because development stopped, TERN-601 was never manufactured or sold as a product, and no legitimate supply for personal use has ever existed.
Regulatory and Developmental Status
TERN-601 was never approved by the FDA or any other regulatory authority. Its clinical development was discontinued by Terns Pharmaceuticals in October 2025, following the Phase 2 (FALCON) trial’s liver enzyme safety findings, before any regulatory filing was made. The company stated it would not advance TERN-601 or invest further in its metabolic-disease portfolio. This status is considered final based on the sources reviewed for this page as of 2026-09-27, though readers should check Terns Pharmaceuticals’ own communications for any updates.
Frequently Asked Questions
What is TERN-601?
TERN-601 was an investigational, once-daily oral small-molecule GLP-1 receptor agonist developed by Terns Pharmaceuticals for obesity. Its clinical development was discontinued in October 2025 due to liver safety findings.
How does TERN-601 work?
It activated the GLP-1 receptor, reducing hunger and increasing fullness, similar in mechanism to injectable GLP-1 drugs but delivered as a once-daily pill.
What dosage was studied for TERN-601?
Phase 1 tested 240 mg, 500 mg, and 740 mg once daily over 28 days. Phase 2 tested 250 mg, 500 mg (two titration schedules), and 750 mg once daily over 12 weeks. The 500 mg standard-titration dose produced the largest weight-loss effect.
Is there a dosage that commonly circulates online?
500 mg once daily is the figure most associated with TERN-601’s best efficacy result, but this comes from a peer-reviewed clinical trial publication, not community or vendor sources — TERN-601 never circulated in research-chemical channels and, since it was discontinued, is not available for purchase anywhere.
How frequently was TERN-601 dosed?
Once daily, by mouth, in every study.
What routes were reported?
Oral only.
How long did reported protocols last?
Phase 1 ran 28 days; Phase 2 (FALCON) ran 12 weeks. No longer trials were completed before the program was discontinued.
Has TERN-601 been studied in humans?
Yes, in a completed and peer-reviewed Phase 1 and Phase 2 program — one of the better-documented compounds among discontinued oral GLP-1 candidates.
What side effects have been reported?
Common gastrointestinal effects (nausea, vomiting, constipation, diarrhea), and — the reason development stopped — liver enzyme elevations in three Phase 2 participants, two assessed as consistent with drug-induced liver injury.
Is TERN-601 approved?
No. It was never approved, and its development was discontinued before any regulatory filing.
How strong is the evidence?
Relatively strong for an investigational compound — both the efficacy and safety findings come from a peer-reviewed, published Phase 1/Phase 2 clinical trial report, not just company press releases.
What remains unknown?
Whether the liver enzyme elevations were truly caused by TERN-601 or were coincidental, whether the effect was dose-dependent, and how weight loss and safety would have evolved beyond 12 weeks — none of this will now be resolved, since the program has ended.
Bottom Line
TERN-601 is a discontinued investigational oral small-molecule GLP-1 receptor agonist. It is one of the more thoroughly documented compounds in this pipeline category, with peer-reviewed, published Phase 1 and Phase 2 human data showing statistically significant weight loss (up to about 4.6% placebo-adjusted at 12 weeks, at a 500 mg once-daily dose). What ended its development was not a lack of efficacy but a liver safety signal: three Phase 2 participants developed elevated liver enzymes after treatment, two consistent with drug-induced liver injury, prompting Terns Pharmaceuticals to discontinue the entire program in October 2025 rather than investigate further. Dosage information “circulating” about TERN-601 is limited to these same peer-reviewed clinical trial figures — it never reached community or vendor channels, and no supply exists since the drug was never brought to market. Major limitations include the short 12-week trial duration and the fact that causality for the liver findings, while judged concerning enough to end the program, was not conclusively proven in every case. TERN-601 is discontinued, not approved, and not in active development.
Sources
- Garvey WT, et al. — “Oral GLP-1RA TERN-601 for Adults With Obesity/Overweight: Placebo-Controlled, Multiple-Ascending-Dose, Phase 1 and 2 Studies” — Obesity (Silver Spring), 2026 — PubMed
- Terns Pharmaceuticals — “Terns Pharmaceuticals Reports Topline 12-week Data from its Phase 2 Trial Evaluating Oral GLP-1 Receptor Agonist TERN-601 in Obesity” — GlobeNewswire, October 2025 — Company press release
- Terns Pharmaceuticals — “Terns Pharmaceuticals Announces Positive Phase 1 Clinical Trial Results with TERN-601 Once-Daily Oral GLP-1R Agonist for the Treatment of Obesity” — GlobeNewswire, September 2024 — Company press release