Kinesin Spindle Protein (KSP) Inhibitors. 9. Discovery of (2S)-4-(2,5-Difluorophenyl)-N-[(3R,4S)-3-fluoro-1-methylpiperidin-4-yl]-2-(hydroxymethyl)-N-methyl-2-phenyl-2,5-dihydro-1H-pyrrole-1-carboxamide (MK-0731) for the Treatment of Taxane-Refractory Cancer

Abstract

Inhibition of kinesin spindle protein (KSP) is a novel mechanism for treatment of cancer with the potential to overcome limitations associated with currently employed cytotoxic agents. Herein, we describe a C2-hydroxymethyl dihydropyrrole KSP inhibitor ( 11) that circumvents hERG channel binding and poor in vivo potency, issues that limited earlier compounds from our program. However, introduction of the C2-hydroxymethyl group caused 11 to be a substrate for cellular efflux by P-glycoprotein (Pgp). Utilizing knowledge garnered from previous KSP inhibitors, we found that beta-fluorination modulated the p K a of the piperidine nitrogen and reduced Pgp efflux, but the resulting compound ( 14) generated a toxic metabolite in vivo. Incorporation of fluorine in a strategic, metabolically benign position by synthesis of an N-methyl-3-fluoro-4-(aminomethyl)piperidine urea led to compound 30 that has an optimal in vitro and metabolic profile. Compound 30 (MK-0731) was recently studied in a phase I clinical trial in patients with taxane-refractory solid tumors.

K858, a Novel Inhibitor of Mitotic Kinesin Eg5 and Antitumor Agent, Induces Cell Death in Cancer Cells

“…Similar to microtubule-targeted drugs, Eg5 inhibition leads to mitotic arrest and cell death (10,11). The chemical structure of K858 is different from many previously identified Eg5 inhibitors (9)(10)(11)(12)(13)(14)(15)(16), and our data indicate that it preferentially exerts antitumor effects while preserving normal cells, thus potentially inducing fewer adverse events. In support of this, K858 had no effect on microtubule organization and did not induce DNA damage, aberrant chromosome segregation, or aneuploid formation.…”

“…In particular, Eg5, a key molecule involved in the formation of bipolar spindles (8), is one of the most attractive target enzymes in antimitotic drug discovery, and several chemotypes of small molecule Eg5 inhibitors have been reported (9)(10)(11)(12)(13)(14)(15)(16). The Eg5 inhibitors S-trityl-L-cystein (10), CK0106023 (11), ispinesib (12), KSP-IA (13), and MK-0731 (14) were identified in a biochemical screen for inhibitors of the ATPase activity of Eg5. Monastrol (15) and HR22C16 (16) were selected using a phenotypebased screen for antimitotic agents and were subsequently identified as Eg5 inhibitors.…”

Intratumor RNA interference of cell cycle genes slows down tumor progression

“…Several inhibitors of KSP have progressed into clinical trials and many others are in preclinical development. [30][31][32] Similarly, PLK1 inhibitors have moved into clinical studies in patients with locally advanced or metastatic cancers, 33 and in vitro studies have shown that the combination of PLK1-specific siRNAs with modern breast cancer drugs could represent rational combinations to improve the sensitivity in a synergistic manner. 34 Using luciferase as a biomarker, we first showed in vitro and in vivo KD (in tumor tissue) of luminescence (Figure 1a).…”

The Discovery and Development of Eg5 Inhibitors for the Clinic

“…The benzyl group occupies a hydrophobic pocket bounded by Trp 127, Pro 137, Val 210 and Tyr 211, and is further enclosed by the benzamide moiety of ispinesib, with which it forms an intramolecular edgeto-face stacking interaction. The isopropyl group lies in a small hydrophobic patch between the backbones of Leu 214/Glu215 and Tyr 211, while the quinazolinone core is situated in deeper hydrophobic pocket formed by Ile 136, Leu160, Leu171, [ 13 ]; ( b ) MK0731 binding to Eg5 (PDB entry 3CJO) [ 25 ]; ( c ) EMD534085 binding to Eg5 (PDB entry 3L9H) [ 26 ]; ( d ) STLC binding to Eg5 (PDB entry 3KEN) [ 27 ]. The ligands are coloured by atom type: green (C), cyan (F), dark green (Cl), yellow (S), blue (N) and red (O).…”

“…While working to overcome limitations in in vivo effi cacy and affi nity for the hERG channel, the researchers at Merck revisited the simpler dihydropyrrole scaffold of 3.13 (Table 2.1 ) [ 25 ]. During lead optimisation, they had noted that a hydroxymethyl substituent was a viable alternative to the solubilising propylamine side chain introduced later in the program which did not display the increased propensity for hERG channel interactions.…”