An Endocrine News roundup of the week’s pharmaceutical news, breakthroughs, and general information. *
FDA Approves First Treatment for MCT8 Deficiency
On Sept. 28, the U.S. Food and Drug Administration (FDA) approved Emcitate (tiratricol) tablets for oral suspension to treat peripheral thyrotoxicosis (excess thyroid hormone levels in the blood that causes symptoms, such as rapid heart rate, increased blood pressure and adverse effects on metabolism) in patients with MCT8 deficiency, also known as Allan-Herndon-Dudley syndrome.
Emcitate is the first therapy approved by the FDA to treat symptoms of this very rare, devastating genetic disease. This approval reflects the FDA’s dedication to patients with rare genetic diseases, many of whom have serious unmet medical needs.
MCT8 deficiency is a rare genetic disorder that primarily affects males. The condition is caused by a faulty gene that provides instructions for making the MCT8 transporter, a critical protein responsible for carrying thyroid hormone into the brain. Because thyroid hormone cannot cross the blood-brain barrier without the MCT8 transporter, the brain receives too little of this hormone, while excessive levels of the hormone build up in the bloodstream. Many patients with MCT8 deficiency experience a range of debilitating effects, including the inability to walk or sit independently, absent or severely limited speech, intellectual disability, feeding difficulties and chronic stress on the heart and metabolism.
“The challenge in treating MCT8 deficiency has always been that the protein needed to deliver thyroid hormone into cells is the one that isn’t working,” said Endocrine Society member Hylton V. Joffe, MD, MMSc, director of the Office of Cardiology, Hematology, Endocrinology, and Nephrology in the FDA’s Center for Drug Evaluation and Research. “This drug sidesteps that problem, as its active ingredient, tiratricol, can enter cells on its own without relying on the broken transporter, leading to a decrease in the elevated blood thyroid hormone levels.”
The effectiveness of Emcitate was evaluated in two clinical studies in patients ranging in age from infants to adults, including an international, multi-center, randomized, placebo-controlled trial (NCT05579327) and a longer-term open-label study. Across both studies, patients treated with Emcitate had reductions in excess thyroid hormone levels in the bloodstream and improvements in cardiovascular and metabolic symptoms impacted by thyroid levels, such as systolic blood pressure and heart rate.
Emcitate is taken once daily as a liquid suspension, either by mouth or through a feeding tube for patients who have difficulty swallowing, making it accessible for patients with a wide range of abilities. The most common side effects were diarrhea, vomiting, rash and excessive sweating. Patients taking another thyroid medication should talk to their healthcare provider before starting Emcitate, as the two should not be used together.
Emcitate was granted Orphan Drug, Rare Pediatric Disease, Fast Track and Breakthrough Therapy designations as well as Priority Review. The approval of Emcitate was granted to Egetis Therapeutics US Inc.
FDA Accepts sNDA and Grants Priority Review to Bayer’s Lynkuet® (elinzanetant) for a New Indication for the Treatment of Moderate to Severe Vasomotor Symptoms Due to Endocrine Therapy Related to Breast Cancer
On Sept. 28, Bayer announced that the U.S. Food and Drug Administration (FDA) has accepted the company’s supplemental New Drug Application (sNDA) and granted Priority Review designation for Lynkuet® (elinzanetant) under investigation for the treatment of moderate to severe vasomotor symptoms (VMS, also known as hot flashes) in women receiving endocrine therapy for treatment of breast cancer.
First approved by the FDA in October 2025 for the treatment of moderate to severe VMS due to menopause, Lynkuet is a dual neurokinin (NK) targeted therapy, neurokinin 1 (NK-1) and neurokinin 3 (NK-3) receptor antagonist.
“Currently, there are no FDA approved treatment options for moderate to severe vasomotor symptoms associated with endocrine therapy in patients with HR+ breast cancer in the U.S. This treatment gap underscores an important unmet medical need for this population,” said Kristie Baisden, DO, vice president, U.S. Medical Affairs, Women’s Health at Bayer. “As a global leader in women’s healthcare, this priority review is an important milestone for Bayer and underscores our commitment to women’s health and making treatment options available. We look forward to working closely with the Agency as they review the application.”
The sNDA for Lynkuet is based on results of the Phase III OASIS-4 trial. Key details and findings from the study include:
- The OASIS-4 study was a 52-week, double-blind, randomized placebo-controlled Phase III interventional study conducted at 90 sites outside of the U.S. A total of 474 women 18 to 70 years of age with moderate to severe VMS associated with endocrine therapy for HR+ breast cancer or its prevention were randomized 2:1 to elinzanetant (n=316) for 52 weeks or placebo for 12 weeks, followed by elinzanetant for 40 weeks (n=158).
- Lynkuet met the primary endpoints of reducing the mean daily frequency of moderate to severe VMS symptoms from baseline to week 4 and 12 compared to placebo, in women receiving endocrine therapy for treatment or prevention of HR+ breast cancer.
- Common adverse events during the trial were headache, fatigue, and somnolence. During the placebo controlled period of the study for the first 12 weeks, somnolence, fatigue, and diarrhea were reported more frequently with elinzanetant than with placebo.
- The key findings were presented at ASCO 2025 and simultaneously published in the New England Journal of Medicine (NEJM) in June 2025.
In the U.S., breast cancer accounts for 30% of all cancers in women, with HR+ cancers comprising approximately 70% of all breast cancer cases. HR+ breast cancer treatment guidelines from the American Society of Clinical Oncology recommend endocrine therapy, with a minimum duration of use of five years, with potential extension to 10 years based on cancer type and other clinical considerations. Hot flashes can be a common side effect of endocrine therapy treatment.
“Endocrine therapy is a standard of care for many women facing HR+ breast cancer and can commonly cause side effects such as vasomotor symptoms,” said OASIS-4 primary investigator Fatima Cardoso, MD, FESMO director, Breast Unit, Centre Antoine Lacassagne and Advanced Breast Cancer (ABC) Global Alliance, Nice, France. “It’s important that we continue to learn more about vasomotor symptoms due to endocrine therapy as part of supporting women throughout their breast cancer care journey.”
The October 2025 FDA approval was supported by data from three Phase III clinical trials (OASIS-1, OASIS-2 and OASIS-3) evaluating the safety and efficacy of Lynkuet for the treatment of moderate to severe hot flashes due to menopause.
FDA Approves Lilly’s Onswik™ (insulin efsitora alfa-gobe) for Adults Living with Type 2 Diabetes
On Sept 24, Eli Lilly and Company announced the U.S. Food and Drug Administration (FDA) approval of Onswik™ (insulin efsitora alfa-gobe), a once-weekly basal insulin, indicated along with diet and exercise to control high blood sugar in adults with type 2 diabetes. Onswik is designed to deliver steady basal insulin levels over a full seven days.
“For over a century, Lilly has been developing insulins that transformed diabetes care for millions of people worldwide, but delays in initiating treatment and the burden of daily injections can have a real impact on patients’ day-to-day experience managing type 2 diabetes,” said Kenneth Custer, PhD, executive vice president and president, Lilly Cardiometabolic Health. “Onswik offers a new once-weekly basal insulin option for patients and reflects our continued commitment to deliver innovative treatment options that expand choice and provide greater flexibility in how people manage type 2 diabetes.”
This is the fourth global approval for Onswik for adults with type 2 diabetes, following regulatory actions from the European Medicines Agency (EMA), Mexico’s Federal Commission for the Protection against Sanitary Risks (COFEPRIS) and Japan’s Pharmaceuticals and Medical Devices Agency (PMDA).
The FDA approval is based on data from the QWINT Phase 3 clinical trials, which evaluated the safety and efficacy of once-weekly Onswik in over 3,400 adults with type 2 diabetes. In each QWINT trial, once-weekly Onswik met the primary endpoint of non-inferior A1C reduction from baseline that was comparable to insulin glargine U-100 (glargine) or insulin degludec U-100 (degludec).
In these clinical trials, Onswik demonstrated an overall safety profile similar to the daily basal insulins studied. Onswik should not be used by people who have type 1 diabetes due to increased risk of severe hypoglycemia (low blood sugar). Common side effects of Onswik include low blood sugar, allergic reactions, reactions at the injection site, skin thickening or pits at the injection site (lipodystrophy), itching, rash, swelling of hands and feet, and weight gain. Please see Indication and Safety Summary below and full Prescribing Information and Patient Information.
Around one in eight Americans live with diabetes, and most of them have type 2 diabetes. Globally by 2030, over 510 million people are expected to live with the disease and 38 million of these are expected to use insulin.8 Insulin remains an important treatment option for many people with type 2 diabetes who do not achieve glycemic goals with other therapies.
The Onswik™ KwikPen® will be available in the U.S. in the coming months in two concentrations: 500 units/mL (contains 1,500 units total) and 1,000 units/mL (contains 3,000 units total).
For more information about Onswik, please visit www.onswik.lilly.com.
