#4033 rapid complement inhibition with the c5 inhibitor crovalimab: a timing analysis using animal model and composer trial data

Abstract Background and Aims Atypical haemolytic uraemic syndrome (aHUS) is a life-threatening disease, characterised by acute kidney injury, thrombocytopenia, and microangiopathic haemolytic anaemia due to complement dysregulation. Currently approved treatments for aHUS include the anti-complement C5 monoclonal antibodies eculizumab and ravulizumab. Although currently approved therapeutic options are effective at both inhibiting complement-mediated thrombotic microangiopathy (TMA) and improving renal function, the regular intravenous (IV) infusion dosing regimens impose a significant treatment burden, particularly in paediatric patients (pts) with aHUS, who may need dialysis in the future due to chronic kidney injury and would benefit from preservation of vascular access. Crovalimab is a novel monoclonal antibody developed against complement C5, engineered to allow for small volume subcutaneous (SC) self-injection every 4 weeks, in a weight-based dosing regimen [1]. In the adaptive Phase I/II COMPOSER trial (NCT03157635) evaluating crovalimab in pts with paroxysmal nocturnal haemoglobinuria (PNH), that, like aHUS, is a complement disorder characterised by uncontrolled complement activation, crovalimab has shown maintained disease control and was well tolerated after a median exposure of 3 years. Further, a Phase III study evaluating crovalimab in previously untreated pts met its primary efficacy endpoints [2]. The efficacy and safety of crovalimab are currently being evaluated in adult and paediatric pts with aHUS, either treatment-naive or switching from another complement inhibitor, in the ongoing Phase III single-arm COMMUTE-a and COMMUTE-p trials [3]. Due to the rapidly progressing nature of aHUS, pts experiencing a TMA require rapid suppression of complement activation upon diagnosis to shut down the complement cascade and avoid further kidney deterioration and organ damage. Here, data from in vivo models and the COMPOSER trial were used to determine the time to complete complement inhibition after first crovalimab IV dose. Method Crovalimab's ability to suppress C5 function and complement activity rapidly was initially studied in in vivo models of cynomolgus monkeys. This study assessed the pharmacokinetics and pharmacodynamics of crovalimab in these monkeys after a single IV or SC dose. As part of this study, four animals per group were evaluated with single 4 mg/kg IV and 20 mg/kg IV doses. Crovalimab was also evaluated in the four-part, Phase I/II COMPOSER trial. Part 2 (n = 10) and Part 4A (n = 8) enrolled pts with PNH who were naive to complement inhibition. Pts in Part 2 received crovalimab 375 mg IV on Day 1, 500 mg IV on Day 8, 1000 mg IV on Day 22 and 170 mg SC weekly from Day 36 for 20 weeks. Pts in Part 4A received an optimised crovalimab dosing regimen of 1000 mg IV on Day 1, 340 mg SC on Days 2, 8, 15, and 22 and 680 mg SC Q4W from Day 29 onwards for 20 weeks. Crovalimab concentration, free C5 and complement activity were measured using validated assays in cynomolgus monkeys and in pts with PNH. Results Compared with baseline values in cynomolgus monkeys, a single crovalimab IV dose of 4 mg/kg reduced mean free C5 concentration by 99.6% and terminal complement activity by 81.4%, within 5 minutes after administration. In treatment-naive pts from COMPOSER Parts 2 and 4, mean free C5 concentration dropped to below 1 μg/mL, indicating a high level of target engagement within 1–6 hours from the first IV dose (Figure 1). Correspondingly, inhibition of terminal complement activity was reached within 1 hour, with values near or below the lower limit of quantification (10 U/mL; Figure 2). Complete complement blockade was generally maintained long-term, up to Week 20, in both Parts 2 and 4, regardless of dose. Conclusion Crovalimab induced a complete, rapid, and sustained blockade of terminal complement activity in both non-human primates and pts with PNH, within hours from first dose. The dosing schedule of crovalimab included an initial IV loading dose, allowing for a rapid onset of action, followed by a convenient long-term SC maintenance regimen.