CMS121 Side Effects

Reported CMS121 side effects

Human data CMS121 has only one human study, the phase 1 trial in 99 healthy volunteers, which listed treatment-emergent adverse events as its primary outcome and ran in four parts: single ascending doses in young adults, multiple ascending doses in young adults, multiple doses in volunteers aged 65 to 85, and a food-effect crossover (NCT05318040). A 2025 preprint reports that single doses up to 1,800 mg and repeat doses up to 900 mg a day for 7 days were generally well tolerated, with most treatment-emergent adverse events mild in severity, and that the trial also measured the effect of CMS121 concentration on the corrected QT interval (PMID: 40093210). That report is a preprint and has not been peer reviewed, no results have been posted on ClinicalTrials.gov, and no numbers for individual adverse events are available from either source. Genotoxicity tests CMS121 was negative in a bacterial reverse mutation assay in four Salmonella strains and one Escherichia coli strain, with and without rat liver S9 activation, while all positive controls behaved as expected. It was also negative for structural and numerical chromosomal aberrations in cultured human peripheral blood lymphocytes, with and without S9 activation (PMID: 39422940). Safety pharmacology in animals A functional observation battery in rats given single oral doses of 100, 300 or 1,000 mg/kg found no change in any parameter measured. In telemetered dogs given single oral doses of 10, 30 or 100 mg/kg there were no effects on blood pressure, heart rate or body temperature, and respiratory flow function, respiration rate, tidal volume and minute volume did not change at any dose. The 28-day dog study found no electrocardiogram changes (including no significant increase in the corrected QT interval) at doses up to 100 mg/kg a day (PMID: 39422940). Repeat-dose toxicity in rats and dogs In a 28-day oral study in rats at 100, 300 and 1,000 mg/kg a day there were no deaths and no adverse effects on clinical observations, ophthalmology, clinical pathology or microscopic examination, although male rats gained less weight at the higher doses; the no-observed-adverse-effect level was set at 1,000 mg/kg a day, the highest dose tested. A 14-day study in dogs at up to 300 mg/kg a day produced vomiting, loose and reddish feces, thinness, reduced activity, smaller spleen and thymus, hepatocellular vacuolation, ileal mucosal hemorrhage, renal cortical tubular degeneration and lymphoid depletion at the top dose, which was taken as the maximum tolerated dose. In the 28-day dog study the top dose was cut from 100 to 75 mg/kg a day in the second week because of weight loss and reduced food intake, and at that dose the dogs had vomiting, watery or loose feces, microscopic kidney changes and, in one animal, higher creatinine and blood urea nitrogen; those kidney findings were judged adverse, so the no-observed-adverse-effect level in dogs was 30 mg/kg a day (PMID: 39422940). Gaps No human data exist beyond 7 days of dosing. No published study describes CMS121 in pregnancy, in lactation, in children, in liver or kidney disease, or in combination with any other drug. Because fatty acid synthase is a normal enzyme of lipid synthesis in many tissues, long-term inhibition in people has no safety record.

When to continue, reduce, or stop CMS121

CMS121 contraindications

None can be stated from human data, because the only human study of CMS121 is a phase 1 trial in healthy volunteers and its results have not been published in a peer-reviewed journal (NCT05318040; PMID: 40093210). CMS121 is not an approved medicine: it has no approval anywhere and no established human use. The phase 1 trial excluded volunteers with clinically relevant cardiovascular, hematological, psychiatric, gastrointestinal, hepatic, renal, rheumatologic, autoimmune, endocrine, pulmonary, neurologic or dermatologic disease, anyone with a history of drug-associated skin rash, anyone with a condition or prior surgery that could interfere with drug absorption, anyone taking prescription or non-prescription medicines, herbal remedies or vitamin supplements within 14 days, anyone taking significant inducers of cytochrome P450 enzymes or P-glycoprotein within 28 days, and anyone with an estimated glomerular filtration rate at or below 80 mL/min/1.73 m2, or 70 in the elderly group (NCT05318040). Those exclusions indicate where the sponsor expected uncertainty. In dogs, microscopic kidney changes and higher creatinine and blood urea nitrogen in one dog at 75 mg/kg a day for 28 days were judged adverse and set the dog no-observed-adverse-effect level at 30 mg/kg a day (PMID: 39422940). The mechanism is a reason for caution: the reported target is fatty acid synthase, an enzyme of fatty acid synthesis present in many tissues, and the compound acts by partially inhibiting it (PMID: 32863221). No human study has examined what sustained inhibition does outside the brain.

Why vendor quality drives CMS121 side-effect frequency

Research-compound communities consistently report that adverse-event frequency tracks with source quality. Three reasons: (1) impurity profiles vary by lab (residual synthesis byproducts can trigger reactions); (2) mislabeled mass means actual dose can be 50-150% of stated dose; (3) reconstitution-grade water and capping methodology affect long-term storage stability. COA-verified vendors with published HPLC data minimize all three failure modes. Check a vendor's COA record and Trust Score before you buy.

CMS121 side effects FAQ

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