1.Application of electroretinography (ERG) in early drug development for assessing retinal toxicity in rats.
Huang W1, Collette W 3rd2, Twamley M2, Aguirre SA2, Sacaan A2. Toxicol Appl Pharmacol. 2015 Dec 15;289(3):525-33. doi: 10.1016/j.taap.2015.10.008. Epub 2015 Oct 19.
Retinal ocular toxicity is among the leading causes of drug development attrition in the pharmaceutical industry. Electroretinography (ERG) is a non-invasive functional assay used to assess neuro-retinal physiological integrity by measuring the electrical responses. To directly assess the utility of ERG, a series of studies was conducted following intravitreal and/or iv administration of pan-cyclin-dependent kinase inhibitors: AG-012,986 and AG-024,322 in rats. Both compounds have previously shown to induce retinal toxicity. Retinal injury was evaluated by ERG, histopathology and TUNEL staining. Intravitreal injection of AG-012,986 at ≥ 10 μg/eye resulted in decreases (60%) in ERG b-wave and microscopic changes of mild to moderate retinal degeneration, and at 30 μg/eye led to additional ophthalmic findings. Intravenous administration of AG-012,986 daily at ≥ 5 mg/kg resulted in dose-related decreases (25 to 40%) in b-wave and sporadic to intense positive TUNEL staining.
2.Compromised CDK1 activity sensitizes BRCA-proficient cancers to PARP inhibition.
Johnson N1, Li YC, Walton ZE, Cheng KA, Li D, Rodig SJ, Moreau LA, Unitt C, Bronson RT, Thomas HD, Newell DR, D'Andrea AD, Curtin NJ, Wong KK, Shapiro GI. Nat Med. 2011 Jun 26;17(7):875-82. doi: 10.1038/nm.2377.
Cells that are deficient in homologous recombination, such as those that lack functional breast cancer-associated 1 (BRCA1) or BRCA2, are hypersensitive to inhibition of poly(ADP-ribose) polymerase (PARP). However, BRCA-deficient tumors represent only a small fraction of adult cancers, which might restrict the therapeutic utility of PARP inhibitor monotherapy. Cyclin-dependent kinase 1 (Cdk1) phosphorylates BRCA1, and this is essential for efficient formation of BRCA1 foci. Here we show that depletion or inhibition of Cdk1 compromises the ability of cells to repair DNA by homologous recombination. Combined inhibition of Cdk1 and PARP in BRCA-wild-type cancer cells resulted in reduced colony formation, delayed growth of human tumor xenografts and tumor regression with prolonged survival in a mouse model of lung adenocarcinoma. Inhibition of Cdk1 did not sensitize nontransformed cells or tissues to inhibition of PARP. Because reduced Cdk1 activity impaired BRCA1 function and consequently, repair by homologous recombination, inhibition of Cdk1 represents a plausible strategy for expanding the utility of PARP inhibitors to BRCA-proficient cancers.
3.Toxicity and toxicokinetics of the cyclin-dependent kinase inhibitor AG-024322 in cynomolgus monkeys following intravenous infusion.
Brown AP1, Courtney CL, Criswell KA, Holliman CL, Evering W, Jessen BA. Cancer Chemother Pharmacol. 2008 Nov;62(6):1091-101. doi: 10.1007/s00280-008-0771-1. Epub 2008 May 29.
PURPOSE: Cyclin-dependent kinases (CDKs) play a significant role in the control of cell-cycle progression and exhibit aberrant regulation in various neoplastic diseases. AG-024322 is a potent inhibitor of CDK1, CDK2, and CDK4 that produces cell-cycle arrest and antitumor activity in preclinical models. This study evaluated the toxicity of AG-024322 when given by intravenous (IV) infusion to cynomolgus monkeys, including reversibility of effects.