OrsoBio's TLC-6740 Combination Therapy Achieves 51% Greater Weight Loss Than Tirzepatide Alone in Phase 1b/2a Trial
Key Insights
OrsoBio (search)'s oral mitochondrial protonophore TLC-6740 combined with tirzepatide achieved 13.3% mean weight loss versus 8.8% with tirzepatide alone at 24 weeks, representing a statistically significant 4.5% additional weight loss.
The combination therapy showed continued linear weight decline while tirzepatide monotherapy plateaued at 24 weeks, with no additional safety concerns or treatment discontinuations observed.
TLC-6740 demonstrated improvements in insulin sensitivity, liver health, and body composition without lean mass loss, positioning it as a potential enhancer for incretin therapies.
OrsoBio (search) announced positive topline results from a 24-week Phase 1b/2a trial demonstrating that its oral mitochondrial protonophore TLC-6740, when combined with tirzepatide, achieved significantly greater weight loss compared to tirzepatide monotherapy. The combination therapy met the study's primary and key exploratory endpoints for safety, tolerability, and weight loss.
Trial Design and Patient Population
The randomized, double-blind, placebo-controlled study enrolled 55 adults with obesity (search) (BMI ≥30 kg/m²) without diabetes (search). Participants had a mean baseline weight of 109.2 kg and BMI of 37.5 kg/m². The study compared TLC-6740 180 mg administered orally once daily plus tirzepatide 5 mg weekly subcutaneous injection (N=33) versus placebo plus tirzepatide (N=22) for 24 weeks.
Efficacy Results
At week 24, participants receiving the TLC-6740 combination achieved mean weight loss of 13.3%, compared with 8.8% for tirzepatide alone. The 4.5% mean incremental weight loss with the combination—representing approximately 5.1 kg or a 51% relative increase versus tirzepatide monotherapy—was statistically significant (p=0.018, intention-to-treat).
Notably, while weight loss in the tirzepatide monotherapy arm plateaued at 24 weeks, the combination arm showed continued linear decline, suggesting sustained efficacy potential.
"Our results demonstrate that TLC-6740 can safely enhance weight loss when added to incretin therapy," said Rob Myers, MD, Chief Medical Officer and Head of Development at OrsoBio (search). "The weight loss achieved with TLC-6740 plus low-dose tirzepatide is comparable to that seen with higher-dose tirzepatide in the registrational program, supporting the potential to improve efficacy while maintaining tolerability."
Safety and Tolerability Profile
TLC-6740 was safe and well tolerated in combination with tirzepatide. Adverse event rates, including gastrointestinal events typical of incretin therapy, were similar between groups. No Grade 3 or severe adverse events, treatment discontinuations, or signs of excessive systemic uncoupling (such as fevers) were observed in participants receiving TLC-6740.
Additional Metabolic Benefits
Beyond weight loss, the combination produced significant improvements across multiple metabolic parameters, including insulin sensitivity, liver biochemistry, adiponectin, and high-sensitivity C-reactive protein (hsCRP). An MRI substudy demonstrated meaningful reductions in liver fat and total, visceral, and skeletal muscle adiposity, with no adverse impact on lean mass.
Mechanism of Action and Development Strategy
TLC-6740 is a novel, oral, liver-targeted mitochondrial protonophore designed to increase energy expenditure through targeted hepatic activity. The compound is intended to drive weight loss and improve metabolic health, including insulin sensitivity and lipid metabolism.
"We believe TLC-6740 could broadly enhance therapies that reduce food intake, including GLP-1 receptor (search) agonists and amylin analogs, given its complementary mechanism to increase energy expenditure," Myers noted.
Clinical Development Pipeline
With more than 300 patients dosed for up to 24 weeks across multiple studies, OrsoBio (search) plans to initiate a larger, longer Phase 2b clinical trial evaluating TLC-6740 in combination with an incretin in 2026. The company also plans to present these findings at a scientific conference and pursue peer-reviewed publication in 2026.
OrsoBio (search) is simultaneously advancing TLC-1180, its second-generation mitochondrial protonophore, in an ongoing first-in-human clinical trial. Dosing has been completed in the first two single-dose cohorts, with favorable preliminary safety and tolerability. Preclinical data presented at ObesityWeek® 2025 demonstrated robust weight loss with TLC-1180 as monotherapy and in combination with semaglutide in obese mice and non-human primates.
"Emerging evidence indicates that our protonophore portfolio, as monotherapy or combined with incretins, may address unmet needs in obesity (search) treatment, including greater weight loss with lean mass preservation, improved tolerability, insulin sensitivity, and liver health," said Mani Subramanian, MD, PhD, Chief Executive Officer of OrsoBio (search). "With TLC-6740 and TLC-1180 advancing through clinical development and oral incretins on the horizon, our protonophores are well positioned for use in next-generation treatment regimens, including oral fixed-dose combinations."