Sling Therapeutics Raises $123M Series C to Advance Oral Thyroid Eye Disease Drug
- Sling Therapeutics closed a $123 million Series C financing round led by Forbion, with participation from existing investor TPG Life Sciences Innovations and new investor Sectoral Asset Management.
- Proceeds will fund a Phase 3 trial of linsitinib, an oral small-molecule inhibitor of IGF-1R (insulin-like growth factor 1 receptor), for thyroid eye disease (TED).
- Linsitinib was originally developed by Astellas as a cancer treatment; Sling licensed the compound in 2022 and repositioned it for TED.
- The drug is being developed as an oral alternative to Amgen's infused antibody Tepezza (teprotumumab), the current standard treatment for TED.
- The Phase 3 trial has begun dosing patients, targeting roughly 120 participants, and is evaluating linsitinib's ability to reduce proptosis (eyeball bulging) over a 24-week period.
Tepezza turned thyroid eye disease into a blockbuster franchise despite being an IV-infused biologic — an oral IGF-1R inhibitor now running its own Phase 3 is the first mechanism-matched threat with real clinical data behind it, and Amgen should take notice. The deal's backstory is arguably the sharper story: an Astellas oncology asset shelved, licensed out in 2022, and repositioned for ophthalmology now sits in pivotal testing — the underappreciated-asset playbook every BD team wants to replicate. A $123M Series C landing at Phase 3, not an earlier round, with Forbion leading and new crossover-style investor Sectoral joining incumbent TPG, reads as genuine conviction, not speculative money chasing a hot indication. TED is a small, rare-disease market, but Tepezza proved payers and patients will pay for relief — an oral, self-administered option could expand that funnel further if the proptosis data holds up at 24 weeks.
Sling reels in $123M series C to fund oral Tepezza rival through phase 3 trial ↗