PT-141 Q2 2026: the obesity pivot

The biggest PT-141 story of the quarter has nothing to do with sexual desire. On 31 March 2025 Palatin Technologies reported that BMT-801, a phase 2 trial co-administering bremelanotide with tirzepatide in patients with obesity, met its primary endpoint: the co-administration group lost 4.4% of body weight over eight weeks versus 1.6% on tirzepatide alone (p<0.0001)^[1]. A follow-up release on 17 April showed that low-dose bremelanotide matched tirzepatide on appetite-suppression measures and, more notably, prevented significant weight rebound after tirzepatide was stopped^[2].

The obesity pivot: what BMT-801 showed

BMT-801 enrolled 113 patients, randomising 96 across three arms: bremelanotide plus tirzepatide, tirzepatide alone, and bremelanotide alone. In the co-administration group (n=46), 40% achieved at least 5% weight loss versus 27% on tirzepatide alone; 19% hit 7% versus 0% on tirzepatide alone^[1]. Palatin CEO Carl Spana said the results "exceeded expectations" and described the weight-loss effect as additive, meaning the two drugs together outperformed either alone. No new safety or tolerability concerns emerged in the combination arm.

The appetite data, released two weeks later, added a durability finding. Over 50% of weight lost on tirzepatide or the combination returned within two weeks of stopping treatment. But the bremelanotide-only arm resisted that rebound. Spana characterised it as "low-dose bremelanotide matched tirzepatide in appetite suppression" while "significantly reducing the appetite rebound typically observed after stopping GLP-1/GIP therapy."

The obesity framing is worth pausing on. Bremelanotide activates MC4R, the same hypothalamic receptor tied to appetite and energy balance. The PT-141 mechanism section on the peptide page covers this in detail. In the HSDD clinical programme, the appetite effect was a side observation. In BMT-801, it became the primary endpoint. Palatin is repositioning a known molecule for a different target.

Next-generation MC4R compounds on the clock

Palatin is not stopping at bremelanotide for obesity. The company's pipeline page lists two next-generation MC4R agonists in IND-enabling work: PL7737, an oral small molecule with an IND filing targeted for H1 2026 and phase 1 data expected in H2 2026, and a novel once-weekly injectable peptide with an IND filing expected in H2 2026^[3]. Both are being developed for general obesity, weight-loss maintenance, acquired and congenital hypothalamic obesity, and rare MC4R-pathway diseases including Prader-Willi syndrome.

The oral route matters. Bremelanotide today is a subcutaneous injection, which limits convenience for chronic daily use. An oral MC4R agonist, if it clears phase 1, would enter a market where the biggest GLP-1 competitors (semaglutide via Rybelsus, orforglipron in late-stage trials) are also moving toward oral dosing. Whether a melanocortin-pathway oral drug can compete on efficacy with the incretin class is an open question.

Meanwhile, the HSDD label stays quiet

On the approved-product side, not much changed this quarter. The Vyleesi prescribing information at DailyMed, now under Cosette Pharmaceuticals, was last revised in March 2024^[4]. The 1.75 mg subcutaneous on-demand dose, the 8-dose monthly cap, and the cardiovascular contraindications remain unchanged. No new post-marketing safety signals have appeared. The nausea rate (roughly 40% in the pivotal RECONNECT trials), the transient blood-pressure elevation (approximately 6 mmHg systolic), and the focal hyperpigmentation warning all stand as described on the PT-141 safety section.

On the compounding front, bremelanotide is not among the seven peptides the FDA's Pharmacy Compounding Advisory Committee will review at its 23-24 July 2026 meeting. That session covers BPC-157, KPV, TB-500, MOTs-C, emideltide, Semax and epitalon^[5]. Bremelanotide's status as the active ingredient in an FDA-approved product (Vyleesi) means the compounding pathway is more constrained than for unapproved peptides.

New preclinical work complicates the mechanism story

A January 2025 paper in Neuropharmacology by Borland and colleagues at the University of Minnesota tested bremelanotide in female Syrian hamsters and found that the drug did not act on the VTA-NAc reward circuit and did not enhance the rewarding effects of sexual interactions^[6]. The authors found that MC3R and MC4R mRNA is expressed in dopamine neurons in the ventral tegmental area, but bremelanotide produced no measurable effect on receptor expression or conditioned place preference tied to sexual activity.

Bremelanotide does not act on the VTA-NAc reward circuit and does not enhance the rewarding effects of sexual interactions.

That finding matters because it narrows the plausible mechanism. If bremelanotide is not working through the mesolimbic dopamine pathway that governs reward, the sexual-desire effect likely runs through a different circuit (possibly hypothalamic, possibly elsewhere). The practical implication for clinicians is minimal today, but for Palatin's obesity programme the distinction is relevant: MC4R's role in appetite regulation and MC4R's role in sexual desire may operate through separate central pathways.

What we still do not know

Three gaps are worth flagging. First, the BMT-801 trial was eight weeks with 113 patients. That is enough to signal a direction, not enough to characterise long-term safety of bremelanotide plus tirzepatide co-administration. Larger and longer trials are needed before any regulator would consider the combination for approval.

Second, the next-generation MC4R compounds (PL7737 and the weekly peptide) have not entered human trials yet; their timelines depend on IND clearance. Phase 1 data for PL7737 is expected in H2 2026 according to the pipeline page, but IND-stage timelines shift frequently.

Third, no sponsor has filed for a marketing authorisation for bremelanotide in the EU, EEA or UK, and nothing in the pipeline suggests that will change soon. For the jurisdiction-specific picture, the regulation pages remain the reference. Off-label and grey-market use, especially in men, continues in the absence of any regulatory pathway outside the United States.

Where this lands for PT-141 readers

The quarterly story is a molecule expanding beyond its original label. The RECONNECT phase 3 data from 2019^[7] established bremelanotide for HSDD in premenopausal women. The BMT-801 data from Q1 2025 plants bremelanotide in the obesity combination space alongside the incretin class. And the next-generation MC4R pipeline puts Palatin in the same competitive field as the GLP-1 and dual-agonist programmes that dominate the obesity landscape right now.

Whether the obesity angle proves durable is a question for the phase 1 readouts later this year. For readers tracking bremelanotide for the approved HSDD indication, the label is stable and the drug is available through BlinkRx in the United States. For readers outside the US, lawful access still runs only through unlicensed-medicine or named-patient routes. The PT-141 page reflects the updated picture.