Beyond Weight Loss: 8 Non-GLP-1 Peptides Tackling Rare Disease in 2026

If you've been reading peptide news from major outlets for the last two years, you'd be forgiven for thinking the field is one thing: GLP-1s. Wegovy, Ozempic, Mounjaro, Zepbound, Foundayo, the next-generation incretins. Almost every other peptide therapeutic gets crowded out of the trade-press coverage.

The pipeline tells a different story. Approximately 100 peptide drugs are FDA-approved, and the next-wave clinical pipeline is split roughly 60/40 between obesity-and-cardiometabolic and everything-else. That everything-else category includes some of the most clinically meaningful peptide programs of the next 24 months. Several have Phase 3 readouts pending in 2026 or 2027. Most target indications with no current FDA-approved disease-modifying therapy.

This piece is a survey of eight of those programs — chosen because they span the non-GLP-1 peptide pipeline broadly, have active clinical data, and represent meaningful next-step therapies for patients who currently don't have great options. Some are venture-backed biotech bets; some are existing peptides finding new indications; some are mature platforms tackling targets that small molecules and antibodies haven't cracked.

Amylyx Pharmaceuticals launched a US Expanded Access Program on May 5, 2026 for up to 250 adults with post-bariatric hypoglycemia (PBH) following Roux-en-Y gastric bypass surgery. The investigational compound is avexitide — a first-in-class peptide GLP-1 receptor antagonist. Same receptor as semaglutide and orforglipron, opposite direction of signaling.

PBH is one of those indications most clinicians have never seen and most patients don't know exists until they develop it. Roughly 5-15% of patients who undergo Roux-en-Y gastric bypass develop severe, recurrent hypoglycemic episodes that don't respond to standard nutritional counseling. The mechanism: post-surgery anatomy delivers food rapidly to the distal small intestine, which triggers exaggerated GLP-1 release, which triggers exaggerated insulin secretion, which crashes blood sugar 30-90 minutes after a meal. Avexitide blocks the GLP-1 receptor on pancreatic islet beta cells to flatten that insulin spike.

The Phase 3 LUCIDITY pivotal trial topline reads out in Q3 2026. Avexitide has FDA Breakthrough Therapy Designation for both PBH and congenital hyperinsulinism, Rare Pediatric Disease Designation in congenital HI, and Orphan Drug Designation. If LUCIDITY hits, avexitide becomes the first approved therapy for an indication that has historically been managed with off-label diazoxide and dietary modification — neither of which works well. There's also a competitive dimension: MBX Biosciences' once-weekly imapextide hit Phase 2a proof-of-concept in the same indication in May 2026.

Setmelanotide (IMCIVREE), a melanocortin-4 receptor agonist peptide from Rhythm Pharmaceuticals, was originally approved for rare genetic forms of obesity (POMC, LEPR, PCSK1 deficiency) in 2020. The FDA expanded the label in 2025 for acquired hypothalamic obesity — weight gain caused by damage to the hypothalamus, most commonly from craniopharyngioma surgery in children and young adults. The European Commission added the indication in early 2026, and Japan's PMDA accepted the NDA for review.

The Q1 2026 print on May 5 reported $60.1M in IMCIVREE revenue, up from $37.7M a year earlier — driven entirely by the hypothalamic obesity launch in the US, with 150+ start forms in the quarter. The mechanism is mechanistically distinct from the GLP-1 pathway: setmelanotide signals through MC4R in the hypothalamus to suppress appetite and increase energy expenditure, addressing the specific neuro-endocrine deficit that hypothalamic damage produces. Patients on the drug typically lose 10-15% of body weight in the first year.

The broader Rhythm program had a setback: the EMANATE Phase 3 trial in genetically caused MC4R-pathway diseases missed its primary endpoint in all four independent substudies. The hypothalamic-obesity launch is now the company's lead growth story, with bivamelagon (a second-generation MC4R agonist) and RM-718 backing it up in earlier-stage development. For patients with hypothalamic obesity — most of whom are children and young adults with no other effective therapy — IMCIVREE is currently the only approved option.

Entera Bio's EB613 (oral teriparatide / PTH(1-34) tablet) reached a Phase 3 inflection point in May 2026. The company submitted a streamlined Phase 3 protocol to the FDA in March covering 750 postmenopausal women with osteoporosis, with total hip bone mineral density change at month 12 as the primary endpoint. Trial initiation is now targeted for late 2026, topline H2 2028.

The clinical case for an oral PTH is straightforward. Teriparatide is one of the few osteoanabolic — bone-building, not just bone-loss-slowing — drugs available, with strong fracture-prevention data. The catch is that the approved version (Forteo from Lilly, Bonsity from Pfenex) requires daily subcutaneous injection for up to 24 months, which is the rate-limiting factor on patient uptake. Most osteoporosis patients are postmenopausal women in their 60s, 70s, and 80s; daily self-injection has acceptance and adherence problems in that population.

Entera's N-Tab platform uses absorption enhancers to enable oral peptide delivery, and Phase 2 dose-ranging in 161 patients met both primary (PD/bone-turnover biomarker) and secondary (BMD) endpoints. Topline H2 2028 is realistic for a 12-month bone-density study. If EB613 reaches market, it changes the osteoporosis treatment algorithm in a way that the existing oral-bisphosphonate-vs-injectable-osteoanabolic tradeoff hasn't allowed since teriparatide approval in 2002. A daily oral pill that builds bone could pull treatment forward several years for many patients.

Vertex Pharmaceuticals' Q1 2026 business update confirmed continued enrollment in the multiple-ascending-dose portion of GALILEO, the global Phase 1/2 study of VX-670 in adults with myotonic dystrophy type 1 (DM1). H2 2026 readout. VX-670 is an oligonucleotide linked to a cyclic peptide endosomal-escape vehicle from Entrada Therapeutics' EEV platform — a peptide-conjugate strategy that addresses the central delivery problem in oligonucleotide therapeutics.

DM1 is the most common form of muscular dystrophy in adults, caused by a CTG-repeat expansion in the DMPK gene that produces toxic CUG-containing RNA. The toxic RNA sequesters the splicing factor MBNL1, causing widespread missplicing across hundreds of downstream genes. The disease has no FDA-approved disease-modifying therapy. Symptomatic management — assistive devices, cardiac monitoring, dystrophin-supporting exercise — is the standard of care.

VX-670's mechanism: the oligonucleotide binds CUG-repeat RNA and liberates MBNL1, correcting the upstream missplicing. The cyclic peptide carrier addresses the muscle-tissue delivery problem that has stymied conventional oligonucleotide platforms. If GALILEO produces clean splicing-correction and functional-outcome data in H2 2026, VX-670 becomes the first disease-modifying therapy for DM1 and validates the broader EEV platform for additional indications. Competitive programs in DM1 include PepGen's FREEDOM2-DM1 (Phase 2, recently pivoted as PepGen's lead asset after DMD failure) and Avidity Biosciences' AOC platform.

Crinetics Pharmaceuticals' Palsonify (paltusotine) became the first FDA-approved once-daily oral SST2 nonpeptide agonist for acromegaly in 2025; the European Commission added approval April 27, 2026 across the 27 EU member states plus EEA. The Q1 2026 print on May 7 reported $10.3M in Palsonify net product revenue in its first full commercial quarter, nearly doubling Q4 2025's $5.4M, with 263 unique prescribers (up from 125 at year-end).

Acromegaly is a rare disorder caused by growth-hormone-secreting pituitary tumors, with about 15,000 patients in the US. The previous standard of care relied on injectable somatostatin analogs (Sandostatin/octreotide LAR, Somatuline/lanreotide) administered as long-acting depot injections every 4 weeks. The injections are painful, have GI tolerability issues, and don't bind SST2 selectively — they also hit SST3 and SST5, contributing to off-target effects. Paltusotine binds SST2 selectively and is taken as a once-daily oral pill.

The Phase 3 carcinoid syndrome program is running concurrently — another SST2-driven indication where the same mechanism applies. Crinetics is also developing CRN09682, a first-in-class SSTR2 non-peptide drug conjugate that couples a small-molecule SST2 agonist with monomethyl auristatin E via a cleavable linker for SST2-expressing neuroendocrine tumors. The Phase 1/2 BRAVESST2 trial is enrolling. The Crinetics program — paltusotine for hormone-secreting tumors, CRN09682 for SST2-expressing solid tumors, plus atumelnant in CAH and Cushing's — is one of the most coherent SST2-pathway portfolios in development.

Tonix Pharmaceuticals' Q1 2026 print on May 11 highlighted TNX-1900, an intranasal potentiated oxytocin formulation now in four Phase 2 investigator-initiated studies. The indications span an unusual range: binge-eating disorder, adolescent obesity, bone health in autism spectrum disorder, and arginine vasopressin deficiency (formerly central diabetes insipidus). All four trials are running at Mass General Hospital or the University of Virginia.

Oxytocin gets airtime mostly as 'the love hormone' or as an obstetric drug used to induce labor. Its broader biology is more interesting. Oxytocin signaling modulates feeding behavior, social cognition, bone metabolism, and water balance. Each of the four TNX-1900 indications targets a different one of those functions. The intranasal route bypasses first-pass metabolism and produces measurable CNS exposure — a small but real fraction of dosed oxytocin appears to cross the blood-brain barrier through nasal delivery, which is the basis for the program.

The Phase 2 data hasn't read out yet for any of the four indications. The portfolio is high-risk in the sense that oxytocin's CNS effects have been studied for decades with mixed clinical translation — early Phase 2 results in autism social-cognition were not replicated. But the bone-health and AVP-deficiency arms have stronger mechanistic rationale, and binge-eating disorder is an indication with limited pharmacologic options. None of these are likely to be commercial blockbusters; each represents a meaningful therapy if positive. Tonix's commercial arm — TONMYA (sublingual cyclobenzaprine for fibromyalgia) — generated $3.7M in launch revenue in Q1, providing the cash runway.

PEPITEM — a 14-amino-acid endogenous immunopeptide identified at the University of Birmingham — produced striking preclinical results in inflammatory arthritis models in April 2026, with synthetic PEPITEM reducing joint swelling comparably to infliximab without immunosuppressive side effects. The work, published in Arthritis & Rheumatology, demonstrated that injection of synthetic PEPITEM prevented onset of inflammatory arthritis and reversed established disease in mouse models.

The peptide's mechanism is mechanistically distinct from TNF-blocking biologics. PEPITEM regulates immune-cell trafficking — it's released by B cells and modulates T-cell migration across endothelium. In healthy individuals, PEPITEM levels are appropriately calibrated. In rheumatoid arthritis and other inflammageing conditions, PEPITEM signaling is dysregulated. Restoring it doesn't suppress the immune system the way TNF blockade or JAK inhibition does — it normalizes a specific component of the trafficking decision.

Clinically, PEPITEM is still preclinical with no IND yet filed. The Birmingham group, led by Prof. Helen McGettrick, is working through GMP synthesis and PK studies with academic collaborators including the University of Federico II in Naples. The realistic clinical timeline puts a first-in-human study no earlier than 2027-2028. The reason to flag it now: the inflammageing-peptide category is growing — humanin, MOTS-c, SS-31, PEPITEM, and others — and represents a different therapeutic logic than the immunosuppression playbook that has dominated chronic inflammation for the last 25 years.

Oncopeptides AB announced May 11, 2026 a Type II variation application to the European Medicines Agency to expand the Pepaxti (melflufen) label to third-line treatment of relapsed/refractory multiple myeloma. Pepaxti is one of the two FDA/EMA-approved peptide-drug conjugates currently on market — the other being Novartis's 177Lu-dotatate Lutathera for neuroendocrine tumors.

The Pepaxti mechanism is elegant. Melphalan-flufenamide is a peptide-conjugated form of the alkylating agent melphalan. Aminopeptidases overexpressed in myeloma plasma cells cleave the peptide linker inside the tumor cell, releasing free melphalan intracellularly — concentrating the cytotoxic payload at the disease site and reducing systemic exposure. The label currently covers heavily pretreated (≥4 prior lines) RRMM; the expansion submission would pull it forward to third-line.

The broader peptide-drug conjugate (PDC) category is the fastest-growing peptide-therapeutics subcategory. Six PDCs are in Phase 3, ~96 in development per the late-April ResearchAndMarkets analysis. Avacta's AVA6000 (FAP-Dox) is set for ASCO 2026 presentation in salivary gland cancers; Bicycle Therapeutics' BT8009 (zelenectide pevedotin) is in Phase 2/3 Duravelo for nectin-4-positive urothelial carcinoma; Lilly's CRN09682 SSTR2 non-peptide drug conjugate (via the Crinetics platform) is in Phase 1/2 BRAVESST2. The PDC architecture — tumor-targeting peptide + cleavable linker + cytotoxic payload — fills a niche that ADCs (antibody-drug conjugates) can't always reach, particularly for fast-clearance applications where the long half-life of an antibody is a liability rather than a feature.