Protocol for a multicentre, open-label, dose-escalation phase I/II study evaluating the tolerability, safety, efficacy and pharmacokinetics of repeated continuous intravenous PPMX-T003 in patients with aggressive natural killer cell leukaemia.

introductionAggressive natural killer cell leukaemia (ANKL) is a rare form of NK cell lymphoma with a very low incidence and poor prognosis. While multi-agent chemotherapy including L-asparaginase has been used to treat ANKL patients, they often cannot receive adequate chemotherapy at diagnosis due to liver dysfunction. PPMX-T003, a fully human monoclonal antibody targeting the transferrin receptor 1, shows promise in treating ANKL by helping patients recover from fulminant clinical conditions, potentially enabling a transition to chemotherapy. This study aimed to evaluate the tolerability, safety, efficacy, and pharmacokinetics of repeated continuous intravenous PPMX-T003 in patients with ANKL. METHODS AND ANALYSIS: This multicentre, open-label, dose-escalation phase I/II study will be conducted at nine hospitals in Japan. Patients diagnosed with ANKL (whether as a primary or recurrent disease) and exhibiting abnormal liver function or hepatomegaly due to the primary disease will be included. The primary endpoint is the tolerability and safety of repeated continuous intravenous administration of PPMX-T003 in the first course, based on adverse events and dose-limiting toxicities. PPMX-T003 will be administered as a continuous intravenous infusion every 24 hours for five consecutive days, followed by a 2-day break. Pretreatment will be provided to minimise the risk of infusion-related reactions. Initial doses of PPMX-T003 will be 0.5, 1.0 or 2.0 mg/kg, with subsequent dose increases determined by the Data and Safety Monitoring Committee. The sample size is set at seven participants, with enrolment increased to up to 12 participants if dose-limiting toxicities occur, based on feasibility due to the rarity of ANKL. Descriptive statistics will summarise data according to initial dose, and pharmacokinetic analysis will be conducted based on administered dose. ETHICS AND DISSEMINATION: This study was approved by the institutional review boards at participating hospitals. The results will be disseminated in peer-reviewed journals. TRIAL REGISTRATION NUMBER: jRCT2061230008 (jRCT); NCT05863234 (ClinicalTrials.gov).