IPH4102; An Anti-KIR3DL2 Monoclonal Antibody in Refractory Sezary Syndrome: Results from a Multicenter Phase 1 Trial

Aims: Sezary Syndrome (SS) is the most aggressive form of cutaneous T cell lymphoma (CTCL), characterized with high blood involvement and expression of Killer cell immunoglobulin like receptor 3DL2 (KIR3DL2). IPH4102 is a first-in-class monoclonal antibody that targets KIR3DL2. Very limited effective treatment options are available for SS patients with refractory disease. We conducted a phase 1 study testing IPH4102 in patients with refractory CTCL. Here we report results from the SS subset.

Methods: IPH4102-101 study is a multicenter phase I trial composed of a dose escalation and cohort expansion portions that evaluated IPH4102 in patients with refractory CTCL. Key eligibility criteria included failure of ≥ 2 prior systemic therapies. KIR3DL2 testing was performed for all patients at baseline and at different time points throughout the study. IPH4102 was given Q1w x 4 weeks, followed by Q2w x 10 weeks then Q4w until disease progression or unacceptable toxicity. Primary endpoint is safety. Main 2ry endpoints include best global response (BGR) using the Olsen criteria, progression-free survival (PFS), duration of response (DOR), quality of life (QOL) and biomarker analyses.

Results: The study included 35 SS patients, 20 in the dose escalation and 15 in the cohort expansion, with a median age of 70 years (37-90). Median time from initial SS diagnosis to starting IPH4012 was 22.8 months. Nineteen patients (54%) received IPH4102 as ≥ 4^th line of systemic therapy and 7 (20%) were previously treated with mogamulizumab. Thirteen patients (37%) had lymph node involvement as per investigator assessment and based on radiological examination while 7 patients (20%) had evidence of large cell transformation. KIR3DL2 expression was observed in either skin or blood in 33 patients (94%) and in both in 28 patients (80%). Most common adverse events (AEs) were asthenia (26%), peripheral edema (26%), and fatigue (23%), which were all grade 1-2. Possibly related grade ≥ 3 AEs were observed in 7 patients (20%), and only 2 patients (6%) stopped treatment for an AE. Table 1 shows BGR and response by compartment. Overall response rate was 42.9% [95% CI: 28.0% - 59.1%], with median time to response of 4.8 months. Median DOR and PFS were 5.6 months [95% CI: 3.2-not reached] and 12.8 months [95% CI: 8.1-not reached], respectively. Mogamulizumab pretreated patients showed BGR, median DOR and PFS of 42.9%, 13.8 and 20.9 months, respectively. Quality of life assessment was performed using the Pruritus VAS score andSkinDex29. Patients with CR, PR or SD showed marked improvement overtime of all evaluated parameters including SkinDex29 global, symptoms, emotional, and functional scores. Biomarker analysis showed progressive decrease in CD4/CD8 ratio in responding patients. The decrease of KIR3DL2+ expressing cells in skin evaluated by immunohistochemistry at week 5 and 14 was able to predict BGR (AUC=0.749, 0.714, respectively). Figure 1 shows reduction in KIR3DL2 expressing cells at week 5 and week 14 in a patient who had PR as BGR. To date, 9 patients are still ongoing treatment. Updated clinical and correlative research analyses will be presented at the meeting.

Conclusions: IPH4102 is highly effective in patients with refractory SS. It induces meaningful clinical activity and improves quality of life placing it as an encouraging treatment option for these patients. Further development in SS and other T-cell malignancies is underway.

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