Discovery and Preclinical Study of Novel BTK Degrader HZ-Q1060

Introduction: Bruton's tyrosine kinase （BTK） is a clinical validated drug target for therapy of B cell lymphoma and autoimmune diseases. However, same as other kinase inhibitors, acquired drug resistance, which is the result of BTK C481S mutation, has been observed in patients. So reversible BTK inhibitors were developed to overcome acquired drug resistance of covalent BTK inhibitor. While, in order to have enough efficacy, reversible BTK inhibitors required much higher drug exposure which may lead to higher risk of adverse effect. Hence, it is urgent to develop new technique to overcome drug resistance caused by BTK C481S mutation. Proteolysis-targeting chimeras(PROTAC) is promising new strategy for drug development. PROTAC can achieve sustained target degradation in a catalytical mechanism. So comparing with traditional small molecule inhibitor, PROTAC drug has great advantage in solving acquired drug resistance. Therefore, with the aim of solving acquired drug resistance of 1st generation of BTK inhibitor, we identified a novel BTK-PROTAC HZ-Q1060 based on our in-house DaTProD® platform which is setting up to promote PROTAC development. After a series of evaluations, HZ-Q1060 has been validated as a promising pre-clinical candidate for further clinical development.

Results:

1. HZ-Q1060 can effectively degrade BTK in cancer cell lines and human PBMC, and the half degradation concentration (DC₅₀) in Mino is less than 0.5nM. At the same time, HZ-Q1060 can also induce the degradation of intracellular mutant BTK-C481S protein.

2. HZ-Q1060 has not observed any inhibition and degradation effect on other kinases except BTK, especially kinases that may be related to potential side effects by inhibiting, such as EGFR and TEC.

3. In vitro cancer cell growth inhibition assay, it completely suppressed the cell proliferation of a panel of lymphoma cell lines such as Mino(IC₅₀=0.11nM) and OCI-ly10(IC₅₀=0.28nM).

4. In the PK/PD experiment in mice, a single oral administration of medium dose can degrade more than 80% of BTK within 6 hours, and the degradation effect can be maintained until 24 hours after administration.

5. In the subcutaneous transplanted tumor model of OCI-ly10 mice, the tumor growth was completely inhibited by 3mg/kg of HZ-Q1060 administered orally every day for 14 days, which was equivalent to that of ibrutinib 10mg/kg.

6. In the preclinical pharmacokinetic studies, HZ-Q1060 showed excellent pharmacokinetic properties in different species of animals, included mice, rats and beagle dogs, with long T_1/2 and high dose-normalized AUC.

7. HZ-Q1060 has no significant CYPs inhibitory effect at 10 μM, so it has a low risk of DDI in the future combination therapy.

8. HZ-Q1060 has no inhibitory effect on hERG channel, indicating the compound has a low potential to induce QT prolongation. HZ-Q1060 also shows good safety and tolerance in the preliminary safety evaluation of animals.

Conclusion: In summary, HZ-Q1060 is a potent and selective degrader of BTK with good ADME properties and in vivo efficacy, which makes it suitable for further evaluation in clinical development.

No relevant conflicts of interest to declare.