FDA grants Breakthrough Therapy Designation to Oculis’ privosegtor for optic neuritis

The US Food and Drug Administration has granted breakthrough therapy designation to Oculis’ neuroprotective candidate privosegtor (formerly known as OCS-05) for the treatment of optic neuritis (ON).¹

According to the company, the FDA’s decision was supported by visual‑function results from the Phase 2 ACUITY trial in ON.² Trial results showed privosegtor delivered substantial improvement in LCVA along with consistent anatomical and biological benefits compared with placebo, reinforcing its potential as a neuroprotective treatment across both neuro‑ophthalmic and neurological diseases.

ACUITY randomized 36 eligible patients aged between 18 to 60, with recent onset of unilateral acute optic neuritis with a demyelinating origin, of which 33 patients received privosegtor 2mg/kg/day, 3m/kg/day, or placebo for 5 days in addition to steroid. In addition to achieving the primary safety endpoint, it highlighted neuroprotective structural benefit and the ability to improve visual function in patients suffering from acute optic neuritis.

Patients receiving privosegtor 3 mg/kg/day plus IV methylprednisolone gained an average of 18 letters at 3 months compared with placebo plus IV methylprednisolone. Privosegtor also showed anatomical preservation of retinal and optic nerve structure.

Following a successful meeting with the FDA in 2025, Oculis launched the PIONEER (Privosegtor Investigation in Optic Neuropathies Efficacy Evaluation Research) program³, which includes 3 pivotal trials to support registration plans for privosegtor in ON and a second rare neuro-ophthalmic disease, nonarteritic anterior ischemic optic neuropathy (NAION). The first 2 trials in PIONEER will evaluate privosegtor following the acute onset of optic neuritis in a broad population of patients with multiple sclerosis (MS) and those without MS. PIONEER-1 was initiated in Q4 of 2025, while PIONEER-2 is planned to begin in the first half of 2026.¹

PIONEER-3 will evaluate privosegtor after the acute onset of NAION and is planned to take place in mid-2026. The company noted that PIONEER-3 will share the core design and operational elements with PIONEER-1 and PIONEER-2.

Mark Kupersmith, MD, Chief Medical Advisor, Neuro-Ophthalmology, commented on the FDA decision, saying,¹ “The ACUITY trial delivered truly groundbreaking results, demonstrating for the first time in a single study that a drug candidate consistently improves visual function alongside anatomical and biological evidence of neuroprotective benefit. Significant unmet medical needs remain, as patients with optic neuritis—more often young women and frequently experiencing the first sign of multiple sclerosis—are still at high risk of permanent visual loss.”

Privosegtor has received an orphan drug designation from both the FDA and the European Medicines Agency.

References:

1. Oculis Announces U.S. FDA Breakthrough Therapy Designation Granted to Privosegtor for Treatment of Optic Neuritis. Published January 6, 2026. Accessed January 6, 2026. https://www.globenewswire.com/news-release/2026/01/06/3213346/0/en/Oculis-Announces-U-S-FDA-Breakthrough-Therapy-Designation-Granted-to-Privosegtor-for-Treatment-of-Optic-Neuritis.html

2. Harp MD. Oculis releases positive topline results from phase 2 ACUITY trial evaluating OCS-05 in acute optic neuritis. Published January 6, 2025. Accessed January 6, 2026. https://www.ophthalmologytimes.com/view/oculis-releases-positive-topline-results-from-phase-2-acuity-trial-evaluating-ocs-05-in-acute-optic-neuritis

3. Harp MD. Oculis to launch PIONEER trials for privosegtor in acute optic neuritis and NAION. Published October 6, 2025. Accessed January 6, 2026. https://www.ophthalmologytimes.com/view/oculis-to-launch-pioneer-trials-for-privosegtor-in-acute-optic-neuritis-and-naion