Structure-activity relationship study of beta-carboline derivatives as haspin kinase inhibitors

Abstract

Haspin is a serine/threonine kinase that phosphorylates Thr-3 of histone H3 in mitosis that has emerged as a possible cancer therapeutic target. High throughput screening of approximately 140,000 compounds identified the beta-carbolines harmine and harmol as moderately potent haspin kinase inhibitors. Based on information obtained from a structure-activity relationship study previously conducted for an acridine series of haspin inhibitors in conjunction with in silico docking using a recently disclosed crystal structure of the kinase, harmine analogs were designed that resulted in significantly increased haspin kinase inhibitory potency. The harmine derivatives also demonstrated less activity towards DYRK2 compared to the acridine series. In vitro mouse liver microsome stability and kinase profiling of a representative member of the harmine series (42, LDN-211898) are also presented.

Figure 1

Haspin inhibitors identified by radiometric, thermal stability shift and TR-FRET HTS assays.

Figure 2

Molecular docking of 3 at the ATP-binding site of haspin. Χ¹ and Χ² are the torsion angles that were sampled during the metadynamic calculation.

Figure 3

(A) Free energy surface map from metadynamic calculations sampling two torsion angles (Χ¹ and Χ²) of 9a. Blue and red represent low and high energy conformations, respectively. (B and C) Docking of 9a at the ATP-binding site of haspin for the two conformations of the alkylamine side-chain based on metadynamic calculations.

Figure 4

A Venn diagram highlights kinases selectively inhibited by 3 (red) or 42 (blue) by ≥ 90% at 10 µM. The overlapping region contains only six kinases inhibited by both compounds.

Scheme 1

Reagents and conditions: (a) Br(CH₂)_nNHBoc, Cs₂CO₃, DMF, rt; (b) HCl, MeOH, rt; (c) Br(CH₂)_nNPhth, NaH, DMF, rt; (d) NH₂NH₂•H₂O, EtOH, 65 °C. Phth = phthalimide.

Scheme 2

(a) Me₂NCH=CHNO₂, TFA, rt, 30 min; (b) POCl₃, DMF, 0 °C to rt then MeNO₂, NH₄OAc, 100 °C, 1 h; (c) LiAlH₄, THF, rt; (d) R¹CHO or CF₃CHOH(OEt), MeOH, cat. HCl, rt; (e) MnO₂, 5% Pd/C, DMF, microwave (MW), 150 °C; (f) Br(CH₂)_nNPhth, NaH, DMF, rt; (g) NH₂NH₂•H₂O, MeOH, DCM.

Scheme 3

(a) HBr, AcOH, MW, 130 °C; (b) Tf₂O, i-Pr₂EtN, DCM, 0 °C to rt; (c) MeSO₂NH₂, Pd₂(dba)₃, xPhOS, K₃PO₄, toluene, 110 °C, 1 h; (d) NH₂NH₂•H₂O, MeOH, DCM; (e) Me₂NCH(O-t-Bu)₂, DMF, 120 °C, 1 h; (f) CH₂O, HCO₂H, MW, 150 °C; (g) EtOCHO, MW, 160 °C; (h) LiAlH₄, THF, rt.