The global endocrine community gathered in Chicago for ENDO 2026, the annual meeting of the Endocrine Society, where several biotechnology and pharmaceutical leaders unveiled pivotal data that could redefine treatment standards for rare hormonal disorders. From advancements in congenital adrenal hyperplasia (CAH) and Cushing’s syndrome to novel therapies for acromegaly and hyperinsulinism, the week was marked by a significant shift toward oral, once-daily treatments and precision monoclonal antibodies. The presentations highlighted a recurring theme in modern endocrinology: the pursuit of efficacy that does not come at the cost of patient quality of life, specifically through the reduction of glucocorticoid dependence and the replacement of burdensome injectable regimens with oral alternatives.
Crinetics Pharmaceuticals: Advancing the Standard of Care in CAH and Cushing’s
Crinetics Pharmaceuticals took center stage with comprehensive results from its Phase 2 clinical program for atumelnant (CRN04894), an investigational, once-daily oral adrenocorticotropic hormone (ACTH) receptor antagonist. Atumelnant is designed to block the effects of excess ACTH at the melanocortin type 2 receptor (MC2R) on the adrenal gland, a mechanism that addresses the underlying driver of classic CAH and ACTH-dependent Cushing’s syndrome.
In the TouCAHn Phase 2 trial, Crinetics presented data from Cohort 4, which focused on adults with classic CAH. Unlike previous cohorts where participants maintained their existing glucocorticoid (GC) doses, Cohort 4 participants received 80 mg of atumelnant daily while undergoing a stepwise reduction in their GC intake. The results were particularly striking: despite lowering the GC dose to a target of less than 11 mg/m²/day of hydrocortisone equivalents, participants maintained sustained reductions in androstenedione (A4), 11-hydroxyandrostenedione (11-OHA4), and 11-ketotestosterone (11-KT).
Dr. Alan Krasner, Chief Endocrinologist at Crinetics, emphasized that atumelnant’s ability to suppress adrenal androgens while allowing for reduced steroid use addresses one of the greatest unmet needs in CAH management. Chronic high-dose glucocorticoid therapy, the current standard of care, often leads to long-term complications such as bone loss, metabolic dysfunction, and cardiovascular issues. By blocking ACTH at the receptor level, atumelnant offers a potential path to biochemical control without the collateral damage of exogenous steroid excess.
Furthermore, Crinetics shared results from a Phase 1b/2a study in ACTH-dependent Cushing’s syndrome (ADCS). In a cohort receiving 40 mg daily for ten days, atumelnant demonstrated rapid suppression of cortisol and androgens. These findings have prompted the company to advance atumelnant into late-phase development, with Phase 3 trials for CAH and Phase 2b trials for ADCS already enrolling participants.
Long-Term Stability in Acromegaly: The PALSONIFY Data
In a separate oral presentation, Crinetics provided a two-year update on PALSONIFY (paltusotine), its once-daily oral somatostatin receptor ligand (SRL) for acromegaly. Acromegaly, typically caused by a pituitary tumor, results in excess growth hormone (GH) and insulin-like growth factor-1 (IGF-1), leading to physical disfigurement and systemic complications.
The pooled data from the open-label extension (OLE) trials of PATHFNDR-1 and PATHFNDR-2 confirmed that PALSONIFY provides durable and consistent disease control. In PATHFNDR-1, which transitioned patients from injectable SRLs to oral PALSONIFY, mean IGF-1 levels remained stable at 0.81x the upper limit of normal (ULN) after 96 weeks. In PATHFNDR-2, which included medically untreated patients, IGF-1 levels decreased from a baseline of 1.64x ULN to 0.96x ULN at 72 weeks.
Perhaps most importantly for patients, pituitary tumor volumes remained stable or decreased, and symptoms—measured by the Acromegaly Symptom Diary (ASD)—showed no signs of worsening over the two-year period. The safety profile remained consistent with previous reports, with common adverse events limited to gastrointestinal issues and arthralgia. The success of PALSONIFY represents a significant shift for acromegaly patients, many of whom have spent years enduring painful monthly injections.
Marea Therapeutics: A New Frontier with MAR002
While Crinetics focuses on oral small molecules, Marea Therapeutics introduced a first-in-class approach to acromegaly with MAR002, an allosteric monoclonal antibody targeting the growth hormone receptor (GHR). Presented on June 15, the Phase 1 data suggested that MAR002 might offer a "best-in-disease" profile due to its potency and dosing convenience.
The study reported that MAR002 achieved an IGF-1 suppression of up to 64%, a figure that Dr. Shlomo Melmed of Cedars-Sinai noted exceeds levels seen with many current therapies. Because of its long half-life, MAR002 could potentially be administered via subcutaneous injection as infrequently as once every two weeks or even once a month. This contrasts sharply with the daily injections required by some GHR antagonists currently on the market. Marea Therapeutics expects to initiate a Phase 2/3 study in the coming weeks, positioning MAR002 as a strong contender for patients who do not achieve biochemical control on first-line SRLs.
Recordati Rare Diseases: Real-World Evidence for ISTURISA
Recordati Rare Diseases utilized ENDO 2026 to bolster the clinical profile of ISTURISA (osilodrostat), an oral cortisol synthesis inhibitor. Through four poster presentations, Recordati showcased the long-term safety and efficacy of the drug across the LINC clinical program and real-world settings.
The LINC 6 study, which tracked patients over three years of routine clinical practice, confirmed that osilodrostat maintains sustained biochemical control in patients with endogenous Cushing’s syndrome. Additionally, an analysis of the LINC 3 and LINC 4 studies focused on patient-reported outcomes, revealing significant improvements in physical and mental quality of life.
Recordati also introduced the LINC CARE Phase IV study, which specifically targets patients with Cushing’s syndrome-related hypertension. By focusing on specific comorbidities like hypertension, Recordati is moving toward a more nuanced, patient-centric approach to managing hypercortisolemia. Milan Zdravkovic, Recordati’s Head of R&D, noted that the data reinforces osilodrostat’s role as a cornerstone of long-term management for this complex rare disease.
Ethyreal Bio: Precision Blockade in Thyroid Eye Disease
In the field of thyroid health, Ethyreal Bio presented preclinical data for ETHY-001, a monoclonal antibody designed to treat Graves’ disease (GD) and thyroid eye disease (TED). ETHY-001 targets the thyroid-stimulating hormone receptor (TSHR), which is the primary driver of both conditions.
The preclinical findings presented on June 15 demonstrated that ETHY-001 provides a complete blockade of autoantibody-mediated TSHR activation. This is significant because current TED treatments often target the IGF-1 receptor, which is downstream of the primary pathology. By targeting TSHR directly, Ethyreal Bio aims to treat both the ocular symptoms of TED and the systemic hyperthyroidism of Graves’ disease with a single agent. The company plans to move ETHY-001 into its first human trials in the second half of 2026, offering hope for a more convenient, subcutaneous treatment option.
Rezolute: Tackling the Dangers of Hyperinsulinism
Finally, Rezolute, Inc. highlighted its progress in treating hyperinsulinism (HI), a rare condition characterized by excess insulin production that leads to dangerous, refractory hypoglycemia. The company presented four datasets regarding its lead candidate, ersodetug, a monoclonal antibody that inhibits insulin signaling.
The sunRIZE Phase 3 study results in congenital HI were reviewed, showing that ersodetug significantly reduces the frequency and severity of hypoglycemic events. Furthermore, a case series from an expanded access program (EAP) focused on "tumor HI"—hypoglycemia caused by malignant insulinomas. In this group, 75% of patients who were previously dependent on intravenous dextrose or total parenteral nutrition (TPN) were able to discontinue these intensive interventions after receiving ersodetug.
Dr. Brian Roberts, Chief Medical Officer at Rezolute, noted that these results underscore the "meaningful therapeutic benefit" of ersodetug in preventing the neurological damage associated with chronic low blood sugar. The company’s focus on the natural history of the disease also provided a framework for future health-economic assessments, emphasizing the high cost and clinical burden of untreated HI.
Broader Implications and Analysis
The collective data presented at ENDO 2026 signals a maturing landscape for endocrine therapeutics. The transition from "managing symptoms" to "targeting drivers" is evident in the shift toward receptor antagonists like atumelnant and monoclonal antibodies like MAR002 and ersodetug.
A critical takeaway for the industry is the emphasis on steroid-sparing therapies. In both the CAH and Cushing’s segments, the ability to achieve biochemical normalization while reducing or eliminating the need for exogenous glucocorticoids is becoming the new benchmark for success. This shift addresses a decades-old paradox in endocrinology where the treatment for hormonal excess often resulted in a different, drug-induced hormonal imbalance.
Furthermore, the "oral revolution" in acromegaly, led by paltusotine, suggests that patient preference is now a primary driver of drug development. Biopharmaceutical companies are increasingly aware that even the most effective drug will fail to reach its full potential if the administration is too burdensome for the patient.
As these investigational compounds move toward Phase 3 completion and regulatory filing, the endocrine community anticipates a period of rapid change in clinical guidelines. For patients with CAH, acromegaly, and hyperinsulinism, the data from ENDO 2026 offers a glimpse of a future where rare diseases are managed with greater precision, fewer side effects, and significantly less lifestyle disruption.
