Sling Therapeutics starts the global Phase 3 ORBIT trial of oral linsitinib for thyroid eye disease after positive LIDS results and FDA Fast Track status.
Written By: Kalyani Boharapi,
M.Pharm (Reg. Affairs)
Reviewed By: Pharmacally Editorial Team
Sling Therapeutics has initiated the global Phase 3 ORBIT pivotal trial of oral linsitinib in adults with moderate to severe active thyroid eye disease (TED), advancing the IGF-1R inhibitor into late-stage development. The company is supporting the program with $123 million in Series C financing led by Forbion.
Phase 3 Program Builds on Positive LIDS Results
ORBIT follows the completed Phase 2b/3 LIDS trial, in which linsitinib met its primary endpoint by reducing proptosis, or eye bulging, in patients with moderate to severe TED.
The company also reported a differentiated safety profile in several areas of interest associated with IGF-1R inhibition, including hearing impairment, glycemic changes and menstrual cycle changes. The September 16 financing announcement did not disclose numerical efficacy or safety results from LIDS.
Sling reached alignment with the U.S. Food and Drug Administration on the Phase 3 study design during an End-of-Phase 2 meeting earlier this year.
Oral IGF-1R Therapy Could Change Treatment Administration
Linsitinib is an oral small-molecule inhibitor of insulin-like growth factor 1 receptor (IGF-1R), a validated therapeutic target in TED. IGF-1R signaling contributes to inflammation and tissue expansion around the eye, processes that can drive proptosis and other manifestations of the disease.
The development strategy is notable because the FDA-approved IGF-1R therapy for TED, teprotumumab, is administered by intravenous infusion. Linsitinib is being developed as an oral therapy, potentially offering a less burdensome route of administration if its Phase 3 efficacy and safety findings confirm the earlier results.
TED is an autoimmune disorder most commonly associated with Graves’ disease and hyperthyroidism. Inflammation and expansion of tissues behind the eyes can cause redness, swelling, pain, impaired eye movement and proptosis. Severe disease can threaten vision and produce lasting effects on quality of life.
Treatment may involve medical therapy, orbital surgery or other interventions depending on disease activity and severity. The availability of an oral IGF-1R inhibitor could therefore expand administration options within the treatment pathway.
FDA Grants Fast Track Designation
The FDA has granted linsitinib Fast Track designation for TED, citing the serious nature of the disease and the need for additional treatment options.
Fast Track status enables more frequent interactions between the FDA and sponsor during drug development and can support mechanisms including Rolling Review. A candidate receiving Fast Track designation may also qualify for Accelerated Approval or Priority Review if it meets the applicable regulatory requirements.
Linsitinib has been evaluated in more than 900 patients across 15 clinical trials in multiple diseases, according to Sling.
$123 Million Financing Advances Global Development
The Series C financing was led by Forbion, with participation from existing investor TPG Life Sciences Innovations and new investor Sectoral Asset Management. The proceeds will support continued clinical development of linsitinib, including the global ORBIT Phase 3 program.
Ryan Zeidan, Ph.D., president and CEO of Sling Therapeutics, said the financing strengthens the company’s ability to advance linsitinib toward commercialization while developing an oral treatment option for patients with TED.
Forbion partner Regina Salvat, Ph.D., and Sectoral Asset Management principal François Beaubien, Ph.D., CFA, have joined Sling’s board of directors as part of the financing.
ORBIT Becomes the Key Development Milestone
The initiation of ORBIT moves linsitinib from mid-stage development into pivotal testing. The study will determine whether the proptosis reduction and safety findings observed in LIDS can be reproduced in a larger confirmatory development program.
The next major milestones will include execution of the global Phase 3 trial, generation of confirmatory efficacy and safety data, and subsequent FDA discussions that could support a future marketing application for linsitinib in TED.
Reference
Sling Therapeutics Announces $123 Million Series C Financing to Advance Phase 3 Development of its Oral Small Molecule IGF-1R Inhibitor for Thyroid Eye Disease, Sling Therapeutics, 16 September 2026
A Phase 2b, Study of Linsitinib in Subjects With Active, Moderate to Severe Thyroid Eye Disease (TED) (LIDS), ClinicalTrials.gov ID NCT05276063
About the Writer
Kalyani Boharapi (LinkedIn) is a pharmacy professional and healthcare writer currently pursuing an M.Pharm in Regulatory Affairs at Dr. D. Y. Patil College of Pharmacy, with interests in pharmaceutical regulations, drug development, and healthcare innovation. She has academic exposure to dossier preparation, scientific writing, and regulatory documentation. Kalyani has also completed certification courses in Generative AI, AI in Pharma, and Bioinformatics, and actively participates in pharmaceutical conferences to stay updated with emerging trends and advancements in the healthcare and pharmaceutical industry.