Discovery and Development of a First in Class MKK-4 Inhibitor HRX-215 to Increase Liver Regeneration

As a case study, the development of a first in class MKK4 inhibitor for liver regeneration from target ID to clinical application (Phase I data) will be presented and the chemical structure of the development candidate disclosed. MKK4 has recently been identified as a major regulator in liver regeneration by functional genetic silencing of the dual specific kinase MKK4. The target was validated in various experimental disease models. These data strongly supported the concept, that selective MKK4-inhibition with a small molecule represents a promising and attractive approach for treatment of a complex and multifactorial disease.

In my lecture, I will present on the structure-based development (NMR) and characterization of first-in-class small molecule MKK4 inhibitors (MKK4i). Based on the observation that the approved BRAFV600E inhibitor vemurafenib shows a high affinity to and a moderate functional inhibition of  MKK4, our hit optimization concept included classical iterative SAR-optimization but also a scaffold-hopping approach by changing the core heterocycle from 1H-pyrrolo[2,3-b]pyridine to 1H-pyrazolo[2,3-b]pyridine. Both approaches followed a mandatory multiparameter optimization. In vivo RNAi experiments also revealed that MKK7 and JNK1 are anti-targets and thereby defined the requirements regarding the kinase selectivity. In both series, highly selective MKK4 inhibitors down to a low nanomolar range with an excellent selectivity against MKK7/JNK1 could be obtained. LN3118 was identified as a tool compound with a moderate inhibitory potency against MKK4 (IC₅₀ = 0,2 μM) but an attractive selectivity profile. It was used to validate MKK4 as a druggable target for treatment of liver disease. The PoC in vivo was performed with the „mouse probe“ in hepatectomy models, CCl₄-induced liver injury, alcohol-induced steatosis and CCl₄-induced liver fibrosis.

With our first clinical candidate, HRX215, the effect on liver regeneration was demonstrated after extended hepatectomy in the pig. After 80% liver resection, a significant and impressive acceleration of new liver tissue growth was observed within the first days after surgery. An initial Phase I study in 48 male healthy volunteers paved the way to the now ongoing Phase IIa program to prevent/treat liver failure after extensive oncological liver resections or after transplantation of small grafts.

 

References

1) Zwirner et al., 2024, Cell 187, 1–19 March 28, 2024, 

2) PNAS 2024 Vol. 121 No. 9 e2319492121