7217 Impact of INZ-701 on Bone and Mineral Metabolism Biomarkers and Clinical Outcomes in Adults with ENPP1 Deficiency - Results from 48-week Phase 1/2 Open Label Study

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Abstract Disclosure: K. Gunter: Employee; Self; Inozyme Pharma. Stock Owner; Self; Inozyme Pharma. R.A. Wermers: Research Investigator; Self; Inozyme Pharma. R. Fuhr: Employee; Self; Parexel GmbH. Research Investigator; Self; Inozyme Pharma. D. Schnabel: Research Investigator; Self; Inozyme Pharma. A. Besancon: Research Investigator; Self; Inozyme Pharma. M.A. Nour: Research Investigator; Self; Inozyme Pharma. D. Wenkert: Stock Owner; Self; Inozyme Pharma. Y. Sabbagh: Employee; Self; Inozyme Pharma. Stock Owner; Self; Inozyme Pharma. Background: ENPP1 Deficiency is a rare disorder due to inactivating mutations in the ENPP1 gene that result in low levels of inorganic pyrophosphate (PPi), a critical regulator of mineralization. Subsequent pathologic soft tissue calcification results in severe vascular calcification and ∼50% infant mortality. By early adolescence the majority of survivors develop FGF-23 mediated hypophosphatemic rickets, characterized by bone deformities, short stature, joint/ligament calcification and musculoskeletal pain. No targeted therapy exists for this disease. INZ-701 is a recombinant ENPP1-Fc investigational product. Purpose: To describe the safety, tolerability, immunogenicity, and exploratory efficacy (bone and mineral metabolism biomarkers and clinical outcomes) of INZ-701 in adults with ENPP1 Deficiency through the end of the phase 2 study period (week 48). Methods: Phase 1/2, multicenter, open-label, multiple ascending dose study including three adults in each of three dose cohorts (0.2, 0.6 and 1.8 mg/kg, total N=9) with genetic variants in ENPP1 and PPi <1300 nM (NCT04686175). Participants were dosed subcutaneously on Day 1, then twice weekly from Day 8 to end of study. Data through wk 48 as of July 6, 2023 are included; topline wk 48 data will be presented. Per protocol, participants may continue to receive INZ-701 beyond wk 48. Results: Rapid increase in mean PPi from baseline of 426±407 nM was noted in all patients, reaching the healthy volunteer range within 6 hrs of the first dose with sustained elevation through wk 48. Mean PPi across the 0.2, 0.6 and 1.8 mg/kg dose cohorts from day 32 to wk 48 was 1299±131 nM, 1356±136 nM, and 1282±81 nM, respectively. There were improvements from baseline to wk 48 in mean pooled FGF-23 (-22 pg/mL) and serum phosphate (+0.18 mg/dL), with dose-dependent changes in bone specific alkaline phosphatase consistent with bone healing. DEXA revealed improvements in spine BMD and BMC. There were trends towards improvement in mean % predicted change in 6MWT from baseline to wk 48: cohort 1, 76.7% (SE 10.5) to 85.0% (SE 3.0); cohort 2, 52.2% (SE 10.9 ) to 79.0% (SE 2.9); cohort 3, wk 48 data not available. Improvements were also observed in physician and patient global impression of change score (with no patients deteriorating) and PROMIS pain intensity score. INZ-701 was well tolerated with no drug-related serious or severe (> grade 2) adverse events. Low titers of non-neutralizing anti-drug antibodies (≤160) were observed in 7/9 patients. Long half-life of approximately 126 hours suggests the potential for once-weekly dosing. Conclusions: In adults with ENPP1 Deficiency, INZ-701 was well tolerated with no related serious or severe adverse events. INZ-701 demonstrated a rapid and sustained increase in PPi levels from baseline to week 48 with corresponding improvements in bone mineral biomarkers, functional performance, and patient and physician-reported outcomes. Presentation: 6/3/2024