Chemical formula: C₂₉H₂₇F₃N₆O Molecular mass: 532.56 g/mol PubChem compound: 24826799
Ponatinib inhibits the tyrosine kinase activity of ABL and T315I mutant ABL with IC50 values of 0.4 and 2.0 nM, respectively.
Ponatinib is a potent pan BCR-ABL inhibitor with structural elements, including a carbon-carbon triple-bond, that enable high affinity binding to native BCR-ABL and mutant forms of the ABL kinase.
In cellular assays, ponatinib was able to overcome imatinib, dasatinib, and nilotinib resistance mediated by BCR-ABL kinase domain mutations. In preclinical mutagenesis studies, 40 nM was determined as the concentration of ponatinib sufficient to inhibit viability of cells expressing all tested BCR-ABL mutants by >50% (including T315I) and suppress the emergence of mutant clones. In a cell-based accelerated mutagenesis assay, no mutation in BCR-ABL was detected that could confer resistance to 40 nM ponatinib. Ponatinib elicited tumour shrinkage and prolonged survival in mice bearing tumours expressing native or T315I mutant BCR-ABL.
At doses of 30 mg or greater plasma steady state trough concentrations of ponatinib typically exceed 21 ng/mL (40 nM). At doses of 15 mg or greater, 32 of 34 patients (94%) demonstrated a ≥50% reduction of CRK-like (CRKL) phosphorylation, a biomarker of BCR-ABL inhibition, in peripheral blood mononuclear cells.
Ponatinib inhibits the activity of other clinically relevant kinases with IC50 values below 20 nM and has demonstrated cellular activity against RET, FLT3, and KIT and members of the FGFR, PDGFR, and VEGFR families of kinases.
Peak concentrations of ponatinib are observed approximately 4 hours after oral administration. Within the range of clinically relevant doses evaluated in patients (15 mg to 60 mg), ponatinib exhibited dose proportional increases in both Cmax and AUC. The geometric mean (CV%) Cmax and AUC(0-τ) exposures achieved for ponatinib 45 mg daily at steady state were 77 ng/mL (50%) and 1296 ng•hr/mL (48%), respectively. Following either a high-fat and low-fat meal, plasma ponatinib exposures (Cmax and AUC) were not different versus fasting conditions. Ponatinib may be administered with or without food. Co-administration of ponatinib with a potent inhibitor of gastric acid secretion resulted in a minor reduction in ponatinib Cmax without a reduction in AUC0-∞.
Ponatinib is highly bound (>99%) to plasma proteins in vitro. The blood/plasma ratio of ponatinib is 0.96. Ponatinib is not displaced by concomitant administration of ibuprofen, nifedipine, propranolol, salicylic acid, or warfarin. At daily doses of 45 mg, the geometric mean (CV%) apparent steady state volume of distribution is 1101 L (94%) suggesting that ponatinib is extensively distributed in the extravascular space. In vitro studies suggested that ponatinib is either not a substrate or is a weak substrate for both P-gp and breast cancer resistance protein BCRP. Ponatinib is not a substrate for the human organic anion transporting polypeptides OATP1B1, OATP1B3 and the organic cation transporter OCT-1.
Ponatinib is metabolized to an inactive carboxylic acid by esterases and/or amidases, and metabolized by CYP3A4 to an N-desmethyl metabolite that is 4 times less active than ponatinib. The carboxylic acid and the N-desmethyl metabolite comprise 58% and 2% of the circulating levels of ponatinib, respectively.
At therapeutic serum concentrations, ponatinib did not inhibit OATP1B1 or OATP1B3, OCT1 or OCT2, organic anion transporters OAT1 or OAT3, or bile salt export pump (BSEP) in vitro. Therefore, clinical medicinal product interactions are unlikely to occur as a result of ponatinib-mediated inhibition of substrates for these transporters. In vitro studies indicate that clinical medicinal product interactions are unlikely to occur as a result of ponatinib-mediated inhibition of the metabolism of substrates for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP3A or CYP2D6.
An in vitro study in human hepatocytes indicated that clinical medicinal product interactions are also unlikely to occur as a result of ponatinib-mediated induction of the metabolism of substrates for CYP1A2, CYP2B6, or CYP3A.
Following single and multiple 45 mg doses of ponatinib, the terminal elimination half-life was 22 hours, and steady state conditions are typically achieved within 1 week of continuous dosing. With once-daily dosing, plasma exposures of ponatinib are increased by approximately 1.5-fold between first dose and steady state conditions. Although plasma ponatinib exposures increased to steady-state levels with continuous dosing, a population pharmacokinetic analysis predicts a limited increase in apparent oral clearance within the first two weeks of continuous dosing, which is not considered clinically relevant. Ponatinib is mainly eliminated via faeces. Following a single oral dose of [14C]-labeled ponatinib, approximately 87% of the radioactive dose is recovered in the faeces and approximately 5% in the urine. Unchanged ponatinib accounted for 24% and <1% of the administered dose in faeces and urine, respectively, with the remainder of the dose comprising metabolites.
Ponatinib has not been studied in patients with renal impairment. Although renal excretion is not a major route of ponatinib elimination, the potential for moderate or severe renal impairment to affect hepatic elimination has not been determined.
A single dose of 30 mg ponatinib was administered to patients with mild, moderate, or severe hepatic impairment and to healthy volunteers with normal hepatic function. Ponatinib Cmax was comparable in patients with mild hepatic impairment and healthy volunteers with normal hepatic function. In patients with moderate or severe hepatic impairment, ponatinib Cmax and AUC0-∞ were lower and ponatinib plasma elimination half-life was longer in patients with mild, moderate, and severe hepatic impairment but not clinically significantly different than in healthy volunteers with normal hepatic function.
In vitro data showed no difference in plasma protein binding in plasma samples of healthy subjects and hepatically impaired (mild, moderate and severe) subjects. Compared to healthy volunteers with normal liver function, no major differences in ponatinib PK were observed in patients with varying degrees of hepatic impairment. A reduction of the starting dose of ponatinib in patients with hepatic impairment is not necessary.
Caution is recommended when administering ponatinib to patients with hepatic impairment.
Ponatinib has not been studied at doses above 30 mg in patients with hepatic impairment (Childs-Pugh Classes A, B & C).
No specific studies have been performed to evaluate the effects of gender, age, race, and body weight on ponatinib pharmacokinetics. An integrated population pharmacokinetic analysis completed for ponatinib suggests that age may be predictive of variability for ponatinib apparent oral clearance (CL/F). Gender, race and body weight were not predictive in explaining ponatinib pharmacokinetic intersubject variability.
Ponatinib has been evaluated in safety pharmacology, repeat-dose toxicity, genotoxicity, reproductive toxicity, phototoxicity and carcinogenicity studies.
Ponatinib did not exhibit genotoxic properties when evaluated in the standard in vitro and in vivo systems.
Adverse reactions not observed in clinical studies, but seen in animals at exposure levels similar to clinical exposure levels and with possible relevance to clinical use are described below.
Depletion of lymphoid organs was observed in repeat-dose toxicity studies in rats and cynomolgus monkeys. The effects were shown to be reversible after withdrawal of the treatment.
Hyper-/hypoplastic changes of the chondrocytes in the physis were noted in repeat-dose toxicity studies in rats.
In rats, inflammatory changes accompanied by increases in neutrophils, monocytes, eosinophils, and fibrinogen levels were found in the preputial and clitoral glands following chronic dosing.
Skin changes in the form of crusts, hyperkeratosis, or erythema were observed in toxicity studies in cynomolgus monkeys. Dry flaky skin was observed in toxicity studies in rats.
In a study in rats, diffuse corneal edema with neutrophilic cell infiltration, and hyperplastic changes in the lenticular epithelium suggestive of a mild phototoxic reaction were observed in animals treated with 5 and 10 mg/kg ponatinib.
In cynomolgus monkeys, systolic heart murmurs with no macroscopic or microscopic correlates were noted in individual animals treated with 5 and 45 mg/kg in the single dose toxicity study and at 1, 2.5 and 5 mg/kg in the 4-week repeat-dose toxicity study. The clinical relevance of this finding is unknown.
In cynomolgus monkeys, thyroid gland follicular atrophy mostly accompanied by a reduction in T3 levels and a tendency toward increased TSH levels were observed in the 4-week repeat-dose toxicity study in cynomolgus monkeys.
Ponatinib-related microscopic findings in the ovaries (increased follicular atresia) and testes (minimal germ cell degeneration) in animals treated with 5 mg/kg ponatinib were noted in repeat-dose toxicity studies in cynomolgus monkeys.
Ponatinib at doses of 3, 10, and 30 mg/kg produced increases in urine output and electrolyte excretions and caused a decrease in gastric emptying in safety pharmacology studies in rats.
In rats, embryo-foetal toxicity in the form of post-implantation loss, reduced foetal body weight, and multiple soft tissue and skeletal alterations were observed at maternal toxic dosages. Multiple foetal soft tissue and skeletal alterations were also observed at maternal nontoxic dosages.
In a fertility study in male and female rats, female fertility parameters were reduced at dose levels corresponding to human clinical exposures. Evidence for pre- and post-implantation loss of embryos was reported in female rats and ponatinib may therefore impair female fertility. There were no effects on male rat fertility parameters. The clinical relevance of these findings on human fertility is unknown.
In juvenile rats, mortality related to inflammatory effects was observed in animals treated with 3 mg/kg/day, and reductions in body weight gain were observed at doses of 0.75, 1.5 and 3 mg/kg/day during the pre-weaning and early post-weaning treatment phases. Ponatinib did not adversely affect important developmental parameters in the juvenile toxicity study.
In a two-year carcinogenicity study in male and female rats, oral administration of ponatinib at 0.05, 0.1 and 0.2 mg/kg/day in males and at 0.2 and 0.4 mg/kg/day in females did not result in any tumorigenic effects. The 0.8 mg/kg/day dose in females resulted in a plasma exposure level generally lower or equivalent to the human exposure at the range of dose from 15 mg to 45 mg daily. A statistically significant increased incidence of squamous cell carcinoma of the clitoral gland was observed at that dose. The clinical relevance of this finding for humans is not known.
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