BGB-3111: Small Molecule BTK Inhibitor to Treat B-cell Malignancies
BGB-3111 is a potent and highly selective small molecule BTK inhibitor (Bruton’s Tyrosine Kinase), which we are developing as a monotherapy and in combination with other therapies for the treatment of a variety of lymphomas—the most common form of blood cancer. BGB-3111 blocks the signaling that leads to growth inhibition and cell death in malignant B-cells. We believe, based on our preclinical and clinical data, that BGB-3111 has the potential to be differentiated from ibrutinib in the following aspects:
- Better safety and tolerability – Based on our preclinical studies, we believe BGB-3111 is more selective than ibrutinib in the inhibition of BTK and has less off target inhibition of other kinases, including EGFR, ITK, JAK3, HER2 and TEC, which we believe are associated with ibrutinib toxicity. Results from our preclinical biochemical and cellular assays show that BGB-3111 has similar potency for BTK as compared to ibrutinib while being less active against other kinase targets than ibrutinib, as reflected by the higher dose required to inhibit half the enzymatic activity, or IC50. Based on the selectivity of BGB-3111 relative to ibrutinib, a 2- to 70-fold higher concentration of BGB-3111 is required to achieve similar levels of inhibition in these other targets as compared to ibrutinib. Therefore, BGB-3111 has the potential to be associated with less toxicity. Available data from our completed dose escalation trial indicate that BGB-3111 achieved up to approximately a 7-fold higher exposure level than the approved doses of ibrutinib.
- More sustained inhibition in disease originating tissue – In our preclinical studies, BGB-3111 has demonstrated favorable pharmacokinetic properties. The comparatively high drug level of BGB-3111 in disease originating tissue as demonstrated in the clinic could potentially translate into a more complete and sustainable inhibition and a better quality of response than ibrutinib. Ibrutinib demonstrated a dose-dependent BTK occupancy in PBMCs during its dose-escalation study. However, even at 420 mg, its approved dose for chronic lymphocytic leukemia, ibrutinib did not achieve complete or sustained target occupancy in PBMCs in a significant proportion of patients. In addition, BGB-3111’s favorable safety profile may allow higher doses and more frequent dosing, which could result in more sustained target inhibition. This is currently being investigated in the clinic. At their respective clinically relevant doses in mice (QD for ibrutinib at 50 mg/kg; BID for BGB-3111 at 50 mg/kg), BGB-3111 showed more sustained BTK occupancy in spleen than ibrutinib, albeit similar BTK occupancy in blood.
- Better oral bioavailability – BGB-3111 has shown oral bioavailability of 25–47% in our preclinical animal studies. Based on human data generated in our dose-escalation trial compared to reported data for ibrutinib, BGB-3111 has better oral bioavailability than ibrutinib. Our pharmacokinetic clinical data show a robust and dose-dependent increase in drug exposure and the drug exposure of BGB-3111 at 80 mg QD was comparable to that reported for ibrutinib at 560 mg QD. In addition, the free drug concentration of BGB-3111 at 40 mg QD was comparable to that reported for ibrutinib at 560 mg QD. Lastly, pharmacokinetics data for BGB-3111 suggest that there appears to be far less interpatient variability in drug exposure as compared to ibrutinib.
- Better combinability with ADCC-dependent antibodies – Our preclinical data show that BGB-3111 has less off-target inhibition for ITK than ibrutinib in biochemical and cell models. BGB-3111 displayed a more limited inhibitory effect on rituximab-induced ADCC than ibrutinib in cell-based studies. Our data in a human mantle cell lymphoma xenograft model shows the addition of rituximab to ibrutinib did not improve tumor activity as compared to ibrutinib as a monotherapy. However, the combination of rituximab and BGB-3111 demonstrated improved anti-tumor activity as compared to either as a monotherapy. We believe this may translate into better activity in patients when BGB-3111 is combined with rituximab or other ADCC-dependent antibody therapies.