Talazoparib (Mechanism of Action)

In this article, we will discuss Talazoparib (Mechanism of Action). So, let’s get started.

Mechanism of Action

Talazoparib is an inhibitor of poly (ADP-ribose) polymerase (PARP) enzymes, including PARP1 and PARP2, which play a role in DNA repair. In vitro studies with cancer cell lines that harbored defects in DNA repair genes, including BRCA 1 and 2, have shown that talazoparib-induced cytotoxicity may involve inhibition of PARP enzymatic activity and increased formation of PARP-DNA complexes resulting in DNA damage, decreased cell proliferation, and apoptosis. Talazoparib anti-tumor activity was observed in human patient-derived xenograft breast cancer tumor models that expressed mutated or wild-type BRCA 1 and 2.

Pharmacodynamics

Cardiac Electrophysiology

The effect of talazoparib on cardiac repolarization was evaluated in 37 patients with advanced solid tumors. Talazoparib had no large QTc prolongation (i.e., >20 ms) at the recommended dose.

Pharmacokinetics

After oral administration of 1 mg talazoparib once daily in patients, the recommended dose, the geometric mean [% coefficient of variation (CV%)] of AUC and maximum observed plasma concentration (Cmax) of talazoparib at steady-state was 208 (37%) ng.hr/mL and 16.4 (32%) ng/mL, respectively. The pharmacokinetics (PK) of talazoparib is linear from 0.025 mg to 2 mg (2 times the recommended dose). The median accumulation ratio of talazoparib following repeated oral administration of 1 mg once daily was in the range of 2.3 to 5.2. Talazoparib plasma concentrations reached steady-state within 2 to 3 weeks.

Absorption

Following oral administration of talazoparib, the median time to Cmax (Tmax) was generally between 1 to 2 hours after dosing.

Food Effect

Following a single oral dose of 0.5 mg talazoparib with high-fat, high-calorie food (approximately 800 to 1000 calories with 150, 250, and 500 to 600 calories from protein, carbohydrate, and fat, respectively), the mean Cmax of talazoparib was decreased by 46%, the median Tmax was delayed from 1 to 4 hours, and AUCinf was not affected.

Distribution

The mean apparent volume of distribution of talazoparib is 420 L. In vitro, protein binding of talazoparib is 74% and is independent of talazoparib concentration.

Elimination

The mean terminal plasma half-life (±standard deviation) of talazoparib is 90 (±58) hours, and the mean apparent oral clearance (inter-subject variability) is 6.45 L/h (31.1%) in cancer patients.

Metabolism

Talazoparib undergoes minimal hepatic metabolism. The identified metabolic pathways of talazoparib in humans include mono-oxidation, dehydrogenation, cysteine conjugation of mono-desfluoro-talazoparib, and glucuronide conjugation.

Excretion

Excretion of talazoparib in urine was the major route of elimination. Approximately 68.7% (54.6% unchanged) of the total administered radioactive dose [14C]talazoparib was recovered in urine, and 19.7% (13.6% unchanged) was recovered in feces.