Preclinical Efficacy and Anti-Inflammatory Mechanisms of Action of the Bruton Tyrosine Kinase Inhibitor Rilzabrutinib for Immune-Mediated Disease.

Bruton tyrosine kinase (BTK) is expressed in B cells and innate immune cells, acting as an essential signaling element in multiple immune cell pathways. Selective BTK inhibition has the potential to target multiple immune-mediated disease pathways. Rilzabrutinib is an oral, reversible, covalent BTK inhibitor designed for immune-mediated diseases. We examined the pharmacodynamic profile of rilzabrutinib and its preclinical mechanisms of action. In addition to potent and selective BTK enzyme and cellular activity, rilzabrutinib inhibited activation and inflammatory activities of B cells and innate cells such as macrophages, basophils, mast cells, and neutrophils, without cell death (in human and rodent assay systems). Rilzabrutinib demonstrated dose-dependent improvement of clinical scores and joint pathology in a rat model of collagen-induced arthritis and demonstrated reductions in autoantibody-mediated FcγR signaling in vitro and in vivo, with blockade of rat Arthus reaction, kidney protection in mouse Ab-induced nephritis, and reduction in platelet loss in mouse immune thrombocytopenia. Additionally, rilzabrutinib inhibited IgE-mediated, FcεR-dependent immune mechanisms in human basophils and mast cell-dependent mouse models. In canines with naturally occurring pemphigus, rilzabrutinib treatment resulted in rapid clinical improvement demonstrated by anti-inflammatory effects visible within 2 wk and all animals proceeding to complete or substantial disease control. Rilzabrutinib is characterized by reversible covalent BTK binding, long BTK residence time with low systemic exposure, and multiple mechanistic and biological effects on immune cells. Rilzabrutinib's unique characteristics and promising efficacy and safety profile support clinical development of rilzabrutinib for a broad array of immune-mediated diseases.

Phase 1 clinical trial evaluating safety, exposure and pharmacodynamics of BTK inhibitor tolebrutinib (PRN2246, SAR442168).

Bruton's tyrosine kinase (BTK), expressed in B cells and cells of innate immunity, including microglia, is an essential signaling element downstream of the B-cell receptor and Fc-receptors. Tolebrutinib (PRN2246, SAR442168) is a potent BTK inhibitor that covalently binds the kinase, resulting in durable inhibition with the potential to target inflammation in the periphery and central nervous system (CNS). Tolebrutinib crosses the blood-brain barrier and potently inhibits BTK in microglial cells isolated from the CNS. A first-in-human randomized, double-blind, placebo-controlled study of tolebrutinib was conducted. The trial design consisted of five single ascending dose arms with oral administration of a single dose of 5, 15, 30, 60, and 120 mg (n = 6 per arm, n = 2 placebo), five multiple ascending dose arms with oral administration of 7.5, 15, 30, 60, and 90 mg (n = 8 per arm, n = 2 placebo) over 10 days, and one arm (n = 4) in which cerebral spinal fluid (CSF) exposure was measured 2 h after a single 120 mg dose. Tolebrutinib was well-tolerated in the study and all treatment-related treatment emergent adverse events were mild. Tolebrutinib was rapidly absorbed following oral administration with a rapid half-life of ~ 2 h. Peripheral BTK occupancy was assessed at various timepoints by an enzyme-linked immunosorbent assay-based readout using an irreversible probe. Assessments demonstrated extensive and prolonged peripheral BTK occupancy at steady-state with once daily doses as low as 7.5 mg. Further, CSF exposure was demonstrated 2 h after administration at 120 mg.

Combined therapy with topotecan and gemcitabine in patients with inoperable or metastatic non-small cell lung cancer.

PURPOSE: We conducted a phase I/II trial of topotecan combined with gemcitabine in patients with metastatic or unresectable non-small cell lung cancer (NSCLC) based on preclinical data showing in vitro synergy against an established lung adenocarcinoma cell line. The aim was to determine the maximally tolerated dose (MTD) of topotecan when the gemcitabine dose is held constant, as well the dose limiting toxicity (DLTs) of this combination in NSCLC patients. PATIENTS AND METHODS: Twenty-four patients with stage IIIB or IV NSCLC were treated weekly times 3 with a week break with gemcitabine (1250 mg/m2 over 30 minutes) and topotecan (30 minutes) at varying doses. The starting dose of topotecan was 1.0 mg/m2 and doses were escalated in 0.25-mg/m2 increments until the MTD was achieved. RESULTS: The MTD of gemcitabine/topotecan was 1250 mg/m2 of gemcitabine and 2.00 mg/m2 of topotecan (level 5). Neutropenia was the DLT. Few nonhematologic toxicities were observed. There were 5 (21%) partial responses among 24 patients. The median survival was 22 weeks. Two patients have had prolonged (> 2 year) survival. CONCLUSION: The combination of gemcitabine and topotecan seems to be active against NSCLC with acceptable hematologic toxicity and minimal nonhematologic toxicity. The recommended dose for further study is 1250 mg/m2 of gemcitabine (days 1, 8, 15) and 2.0 mg/m2 of topotecan (days 1, 8, 15) administered every 28 days.