Oculis Holding AG has received the FDA’s agreement for a Special Protocol Assessment (SPA) regarding its phase 3 PIONEER-1 registrational trial evaluating privosegtor for the treatment of optic neuritis (ON).
Start with the basics: Explain SPA.
An SPA is a process where companies request a meeting with the FDA to come to an agreement on the design or size specifications of certain clinical trials for a specific investigational candidate in development.
The timeframe: An SPA request should be submitted (at minimum) 90 days prior to the initiation of a study, after which the FDA will conduct a 45-day review (though it’s not uncommon for the review to extend beyond 45 days).
And the purpose behind this?
Essentially: For the federal agency to decide whether a company’s trial design sufficiently meets the scientific and regulatory requirements needed to support a potential market approval of that investigational asset.
But keep in mind: While an SPA agreement doesn’t necessarily guarantee that the FDA will accept the filing of a candidate’s new drug application (NDA) or biologics license application (BLA), it does (ideally, that is) improve those applications’ quality—or that the respective trial results will support regulatory approval.
Noted. And in Oculis’s case?
The company shared that the FDA’s formal agreement “confirms the design and planned analysis of the PIONEER-1 study are adequate to address the objectives necessary to support a future NDA submission.”
It added that, of course, that NDA package will be “subject to a successful trial outcome and FDA review of the complete submission.”
Of course. Now let’s talk about this candidate.
What it is: A novel peptoid small molecule asset that acts as a serum-glucose corticoid kinase-2 (SGK-2) activator to penetrate the blood-brain and retinal barrier.
- Learn about its mechanism of action, which involves preserving the retina and improving visual function following an acute episode of ON.
The big-picture potential: For privosegtor to become the first neuroprotective therapeutic for acute ON (AON) and non-arteritic anterior ischemic optic neuropathy (NAION).
That would be impressive … has it secured any major FDA designations?
Indeed—two, in fact. Breakthrough Therapy Designation (this past January) as well as Orphan Drug Designation in October 2025.
Nice! And in the context of this SPA, what do we know about its trial?
PIONEER-1 is the first of two pivotal trials within Oculis’s phase 3 PIONEER program (with the third targeting privosegtor’s NAION indication) intended to support registrational plans for privosegtor in ON.
Its purpose: To evaluate privosegtor among a broad population of ON patients (including those with and without multiple sclerosis [MS]).
Its setup: Patients will be followed for 12 months to assess privosegtor’s long-term safety and tolerability.
- Dosing and patient enrollment criteria are expected to mirror those of a previous study: the phase 2 Acute OptiC NeUrITis of DemYelinating Origin (ACUITY) trial (NCT04762017).
And what will be measured?
The primary endpoint is the number of patients achieving at least a 15-letter gain from baseline in low-contrast visual acuity (LCVA) at Month 3.
Oculus noted this to be a “well-established endpoint for clinically meaningful visual function” in ophthalmic trials.
Do we have a timeframe for when this trial will kick off?
As we previously reported, the company originally planned to launch PIONEER-1 in Q4 2025 and run it concurrently with the other two planned trials (PIONEER-2 for ON and PIONEER-3 for NAION) in the PIONEER program.
No word as of yet on an updated schedule for these … so stay tuned.
Will do. But in the meantime, can we get a refresh on privosegtor’s prior data?
For that, we’ll refer back to the aforementioned phase 2 ACUITY trial which, take note, evaluated privosegtor for its AON indication.
The most notable takeaway: Privosegtor met the study’s primary safety endpoint in demonstrating a substantial improvement in vision at Month 3 that was maintained through Month 6 (measured via LCVA).
- For more on its performance, click here.