Safety and Efficacy Results from the Phase I Study of a Novel Dual Covalent and Non-Covalent Next Generation Inhibitor of Bruton's Tyrosine Kinase LP-168 in Patients with Relapsed/Refractory Mantle Cell Lymphoma

Background: Relapsed/Refractory (R/R) mantle cell Lymphoma (MCL) has poor long-term survival compared with other B-cell malignancies. As a result, there is an urgent need for safe and effective treatments, particularly for patients who have progressed on covalent (c) Bruton tyrosine kinase inhibitors (BTKis) therapy. LP-168 is a highly selective, next-generation BTKi with a unique dual binding mode: covalent binding to wild-type BTK and reversible binding to mutated BTK. Pre-clinical data has demonstrated that LP-168 is highly potent in inhibiting C481 mutated BTK. Here, we report the safety and efficacy of LP-168 monotherapy in the R/R MCL patients as part of an ongoing phase 1 study (NCT04993690) in B-cell malignancies.

Methods: This is a Phase 1 first-in-human multicenter open-label study of LP-168 enrolling Chinese patients with B cell Non-Hodgkin Lymphoma (NHL) who have progressed after at least 1 or 2 prior treatments. The study has two parts: Phase 1a: “3+3” dose escalation and Phase 1b: dose expansion in disease-specific cohorts (e.g. R/R MCL, R/R MZL, etc.).

Results: Between 10 August 2021 and 31 May 2023, 33 R/R MCL patients who received at least one dose were enrolled and received LP-168 100mg (n=8), 150mg (n=24), and 200mg (n=1) QD, respectively. Baseline characteristics are summarized in Table 1. The median age was 58 (range, 32-79) years old; 27 (81.8%) were male. 15 (45.5%) subjects had intermediate to high risk disease per MCL International Prognostic Index (MIPI). Median lines of prior therapies were 2 (range, 1-11) with 24.2% refractory to the last prior treatment. All patients have received rituximab or a rituximab-containing regimen. 19 (57.6%) subjects have received at least a cBTKi or cBTKi-containing regimen.

The most common treatment emergent adverse events (TEAEs) (occurring in ≥20% subjects) were platelet count decreased (30.3%), neutropenia and anemia (27.3% each) and COVID-19 (24.2%), most of which were Grade 1. Grade 3 or more TEAEs were seen in 9 (27.3%) subjects. Serious AE (SAE) (lung infection, oral cavity infection and lymphocytosis, all Grade 3) occurred in 3 (9.1%) subjects. Dose interruptions due to AE occurred in 7 patients (21.2%)，but no AE has led to dose adjustment, drug discontinuation or death.

Of 31 efficacy evaluable subjects with median follow up of 5.5 months (range: 2.0-22.5), 24 (77.4%) achieved response including 12 (38.7%) complete metabolic response or complete response (CMR/CR). In addition, 5 (71.4%) out of 7 subjects with blastoid/ pleomorphic variant MCL achieved response (2 CMR/CR, 3 PMR/PR). More importantly, of 17 subjects who had prior cBTKi exposure, 12 (70.6%) responded to LP-168 and 6 (35.3%) achieved CMR. LP-168 also showed efficacy in 2 subjects who have received ≥ 2 cBTKi treatments. Another 2 subjects responded to LP-168 even after disease progression on a cBTKi and a BTK degrader. 5 subjects have achieved progression-free survival (PFS) more than 1 year and are still on treatment (Figure 1).

Conclusion: In this Phase 1 trial, the novel BTK inhibitor LP-168 demonstrated a high CR rate and durable response in heavily pre-treated R/R MCL including blastoid/pleomorphic variant with favorable safety. Moreover, LP-168 could effectively overcome the acquired resistance to prior cBTKi. Based on the safety, PK and preliminary efficacy data from the Phase 1 study so far, we have determined the recommended phase 2 dose (RP2D) for MCL as 150 mg QD. A phase 2 trial of LP-168 in R/R MCL is currently ongoing (NCT05716087).