Pooled Analysis of Safety Data from Clinical Trials of Orelabrutinib Monotherapy in Hematologic Malignancies

Background: Bruton tyrosine kinase (BTK) is one of the key kinases implicated in the pathogenesis of multiple B cell malignancies. Orelabrutinib is a novel, highly selective and potent irreversible BTK inhibitor with minimal activities against other kinases (ITK, EGFR, ERBB2, etc.). As thus orelabrutinib may avoid off-target related adverse events and shall have improved safety profiles comparing to other BTK inhibitors. Here we present the safety profile of orelabrutinib analyzed based on data from 5 ongoing clinical studies in B cell malignancies (Table 1).

Methods: Safety data of 266 patients (pts) from 5 ongoing orelabrutinib monotherapy studies were pooled and analyzed. All pts have been treated with at least one dose of oral orelabrutinib at ≥150 mg daily. The analysis includes the frequency and severity of adverse events (AEs), AEs of special interest, and AEs leading to treatment discontinuation or dose modifications.

Results: Safety data were pooled from 266 pts with median age of 60 years (range 35.0-79.0, 69.2% males). The median duration of exposure was 11.0 months (range 0.2-22.0). The most common (occurring in ≥15% of pts) AEs were neutropenia (28.6%), thrombocytopenia (25.9%), Upper respiratory tract infection (24.4%), leukopenia (18.0%), anemia (16.2%) and rash (15.8%). Treatment related serious AEs (SAEs) were reported in 14.7% pts. The most common treatment related SAEs included thrombocytopenia (3.0%), lung infection (3.0%), pneumonitis (1.9%), anemia (1.1%) and lymphadentis (0.8%), The safety profiles were comparable in pts with various subtypes of B cell malignancies.

It’s noted that orelabrutinib has much less frequency of BTK off-target related adverse events, such as atrial fibrillation, diarrhea, major hemorrhage etc. Among all 266 pts, only one patient was reported with one episode of transient grade 1 atrial fibrillation, and no grade ≥3 atrial fibrillation was observed. Diarrhea of any grade was 7.1% and only one case (0.4%) was reported as grade 3. The major hemorrhage, defined as serious or ≥ G3 bleeding of any site, or central nervous system bleeding of any grade, was rarely observed; as only one case of cerebral hemorrhage, in 65-year-old male patient with more than 10 years hypertension was reported; the other three cases were subcutaneous hemorrhage, vitreous hemorrhage and vitreous hemorrhage/retinal hemorrhage. The later 2 cases of vitreous hemorrhage and/or retinal hemorrhage were resulted from posterior vitreous detachment and macular degeneration and both events were assessed as unlikely related to the treatment. Among 266 pts, the second primary malignancies were reported in only one pt with r/r MCL during orelabrutinib treatment. Grade ≥3 infection occurred in 41 pts (15.4%); most common infections were upper respiratory tract infection and lung infection. Most of the AEs were occurred during the early treatment, the frequency of the new event occurrence was significantly decreased during the later cycles.

Dose reductions due to AEs occurred in 15 pts (5.6%), and treatment discontinuation due to AEs in 5.3% of pts with 2.3% related to orelabrutinib.

Conclusions: Orelabrutinib shows excellent safety profiles and tolerability across various B-cell malignancies in long-term treatment. These data suggested orelabrutinib as a favorable treatment choice including the combinational therapy for B-cell malignancies.

.