Key Takeaways
- • Sling Therapeutics closed a $123 million Series C financing led by Forbion, with participation from existing investor TPG Life Sciences Innovations and new investor Sectoral Asset Management, to advance late-stage development of linsitinib for thyroid eye disease (TED).
- • Linsitinib is an oral small molecule IGF-1R inhibitor positioned as the first and only late-stage oral therapy for TED, offering a differentiated convenience advantage over currently available intravenous and injectable IGF-1R inhibitors.
- • The company has commenced its global Phase 3 ORBIT pivotal trial in adults with moderate to severe active TED, following successful End-of-Phase 2 alignment with the FDA on study design.
- • Prior Phase 2b/3 LIDS trial data demonstrated linsitinib met its primary endpoint of proptosis (eye bulging) reduction with a differentiated safety profile, showing no significant hearing impairment, glycemic changes, or menstrual cycle alterations—key safety concerns for the IGF-1R inhibitor class.
- • Linsitinib received U.S. Fast Track Designation, accelerating regulatory review pathway toward potential commercialization.
Summary
Sling Therapeutics, a clinical-stage biopharmaceutical company based in Ann Arbor, Michigan, announced the close of a $123 million Series C financing on September 16, 2026, to fund late-stage clinical development of linsitinib, an investigational oral therapy for thyroid eye disease. The funding round was led by Forbion, the venture capital firm focused on life sciences, and included participation from TPG Life Sciences Innovations, an existing shareholder, and Sectoral Asset Management, a new investor to the round.
Linsitinib is a small molecule inhibitor of the insulin-like growth factor 1 receptor (IGF-1R), a validated therapeutic target for TED, a serious autoimmune inflammatory condition affecting the eye tissues. The company positions linsitinib as the first and only oral small molecule therapy at an advanced clinical stage for TED, differentiating it from currently available treatment options that require intravenous or injectable administration, thereby offering patients and healthcare providers a more convenient dosing regimen.
The Series C proceeds will support continued advancement of linsitinib through the global Phase 3 ORBIT pivotal trial in adults with moderate to severe active TED. Sling has secured FDA alignment on the trial design following a successful End-of-Phase 2 meeting earlier in 2026, positioning the company for potential regulatory approval and commercialization. Additionally, linsitinib has received U.S. Fast Track Designation, which expedites the FDA review process for therapies addressing serious unmet medical needs.
Clinical validation comes from Sling's previously completed Phase 2b/3 LIDS trial, which met its primary efficacy endpoint of proptosis reduction (a hallmark symptom characterized by eye bulging) in patients with moderate-to-severe TED. Notably, the trial demonstrated a differentiated safety profile compared to other IGF-1R inhibitors, with no significant incidence of hearing impairment, glycemic changes, or menstrual cycle disruptions—safety concerns historically associated with this drug class. This safety data strengthens linsitinib's competitive position and may support its commercial appeal if Phase 3 outcomes are favorable.
Linsitinib is a small molecule inhibitor of the insulin-like growth factor 1 receptor (IGF-1R), a validated therapeutic target for TED, a serious autoimmune inflammatory condition affecting the eye tissues. The company positions linsitinib as the first and only oral small molecule therapy at an advanced clinical stage for TED, differentiating it from currently available treatment options that require intravenous or injectable administration, thereby offering patients and healthcare providers a more convenient dosing regimen.
The Series C proceeds will support continued advancement of linsitinib through the global Phase 3 ORBIT pivotal trial in adults with moderate to severe active TED. Sling has secured FDA alignment on the trial design following a successful End-of-Phase 2 meeting earlier in 2026, positioning the company for potential regulatory approval and commercialization. Additionally, linsitinib has received U.S. Fast Track Designation, which expedites the FDA review process for therapies addressing serious unmet medical needs.
Clinical validation comes from Sling's previously completed Phase 2b/3 LIDS trial, which met its primary efficacy endpoint of proptosis reduction (a hallmark symptom characterized by eye bulging) in patients with moderate-to-severe TED. Notably, the trial demonstrated a differentiated safety profile compared to other IGF-1R inhibitors, with no significant incidence of hearing impairment, glycemic changes, or menstrual cycle disruptions—safety concerns historically associated with this drug class. This safety data strengthens linsitinib's competitive position and may support its commercial appeal if Phase 3 outcomes are favorable.
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