FDA feedback backs urcosimod’s Phase 2b/3 plan for neuropathic corneal pain, defining a meaningful pain endpoint in an unmet field.
A US Food and Drug Administration (FDA) Type C meeting has clarified key elements of the late-phase development pathway for urcosimod, an investigational topical therapy for neuropathic corneal pain (NCP), according to a company press release from OKYO Pharma. The agency indicated that a ≥2-point reduction on a visual analogue scale (VAS) for pain at 12 weeks would be considered clinically meaningful, endorsed the proposed Phase 2b/3 study design and statistical approach, and raised no material concerns regarding chemistry, manufacturing, and controls (CMC). Although the meeting does not constitute regulatory approval, the feedback outlines a potential route toward a pivotal program in a condition with no FDA-approved therapies.
NCP is a chronic ocular pain syndrome attributed to dysfunction or injury of corneal sensory nerves, often with a neuropathic component that may persist despite minimal signs of ocular surface disease. Patients frequently report severe pain, photophobia, and reduced quality of life, and management is challenging because conventional dry eye therapies often provide limited relief.1,2 In this context, FDA feedback on clinically meaningful endpoints and trial design is notable, as it may facilitate the generation of interpretable data in a heterogeneous and under-studied population.
According to OKYO Pharma, the Type C meeting addressed the company’s planned 120-patient Phase 2b/3, multiple-dose, randomized, placebo-controlled study of urcosimod in NCP. The FDA agreed that a change from baseline in the VAS pain score at week 12 could serve as a primary endpoint and explicitly acknowledged that a ≥2-point improvement represents a clinically meaningful treatment effect. The agency also supported the use of the Ocular Pain Assessment Survey (OPAS) as a secondary measure to capture quality-of-life and functional outcomes.
The FDA provided statistical guidance intended to strengthen the robustness of the analysis, noting that if the statistical analysis plan is finalized before unmasking and results are compelling, the data could potentially support substantial evidence of effectiveness at a future end-of-phase meeting. Alignment on CMC strategy was also reported, with no material deficiencies identified. The company previously announced that urcosimod received Fast Track designation and the first investigational new drug (IND) authorization specifically for NCP, although public FDA documentation confirming these designations is limited.3
NCP is increasingly recognized as distinct from nociceptive ocular surface pain associated with tear deficiency or inflammation. Peripheral and central sensitization mechanisms have been described, and patients may have discordance between symptoms and clinical signs.1,4 Current management relies on off-label use of topical corticosteroids, immunomodulators, autologous serum tears, systemic neuropathic pain agents, or neuromodulatory approaches, none of which are approved specifically for NCP. Evidence supporting these strategies is variable and largely derived from small studies or extrapolation from other neuropathic pain conditions.2,5
Urcosimod (formerly OK-101) is described as a lipid-conjugated peptide agonist of chemerin receptor 23 (ChemR23), a G-protein–coupled receptor expressed on immune cells and reported in neuronal and glial tissues. Activation of ChemR23 has been associated with pro-resolving anti-inflammatory signaling in preclinical models.6,7 In ocular research, modulation of inflammatory pathways has been proposed as a means to reduce peripheral sensitization of corneal nerves. However, translation of these mechanisms to clinical benefit in NCP remains to be established.
The company reports positive findings from a small, randomized, double-masked Phase 2 trial in 18 patients with NCP and from a larger Phase 2 trial in dry eye disease, but these data have not yet been published in peer-reviewed journals. As such, interpretation is limited to company-reported outcomes.
FDA concurrence that a ≥2-point VAS improvement is clinically meaningful is consistent with broader pain literature, where similar thresholds have been associated with moderate, patient-perceived benefit.8 Nonetheless, NCP presents unique challenges related to symptom variability, comorbidities, and placebo response. Independent validation of endpoints and reproducibility of effect sizes in adequately powered trials will be critical. Moreover, the supportive role of OPAS may help contextualize pain reduction in terms of daily functioning, an important consideration for clinicians.
The FDA feedback does not guarantee eventual approval, and the proposed Phase 2b/3 study has yet to report results. Key limitations include reliance on company-reported early-phase data, absence of published safety and efficacy findings in NCP, and uncertainty regarding long-term outcomes. The planned trial, if initiated and completed as described, will be an important step in defining the benefit–risk profile of urcosimod in this population.
