Ponatinib after failure of second-generation tyrosine kinase inhibitor in resistant chronic-phase chronic myeloid leukemia.

Ponatinib, the only third-generation pan-BCR::ABL1 inhibitor with activity against all known BCR::ABL1 mutations including T315I, has demonstrated deep and durable responses in patients with chronic-phase chronic myeloid leukemia (CP-CML) resistant to prior second-generation (2G) TKI treatment. We present efficacy and safety outcomes from the Ponatinib Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) and CML Evaluation (PACE) and Optimizing Ponatinib Treatment in CP-CML (OPTIC) trials for this patient population. PACE (NCT01207440) evaluated ponatinib 45 mg/day in CML patients with resistance to prior TKI or T315I. In OPTIC (NCT02467270), patients with CP-CML and resistance to ≥2 prior TKIs or T315I receiving 45 or 30 mg/day reduced their doses to 15 mg/day upon achieving ≤1% BCR::ABL1IS or received 15 mg/day continuously. Efficacy and safety outcomes from patients with CP-CML treated with ≥1 2G TKI (PACE, n = 257) and OPTIC (n = 93), 45-mg starting dose cohort, were analyzed for BCR::ABL1IS response rates, overall survival (OS), progression-free survival (PFS), and safety. By 24 months, the percentages of patients with ≤1% BCR::ABL1IS response, PFS, and OS were 46%, 68%, and 85%, respectively, in PACE and 57%, 80%, and 91%, respectively, in OPTIC. Serious treatment-emergent adverse events and serious treatment-emergent arterial occlusive event rates were 63% and 18% in PACE and 34% and 4% in OPTIC. Ponatinib shows high response rates and robust survival outcomes in patients whose disease failed prior to 2G TKIs, including patients with T315I mutation. The response-based dosing in OPTIC led to improved safety and similar efficacy outcomes compared with PACE.

Retrospective analysis of arterial occlusive events in the PACE trial by an independent adjudication committee.

BACKGROUND: The phase 2 PACE (Ponatinib Ph+ ALL and CML Evaluation) trial of ponatinib showed robust long-term benefit in relapsed Philadelphia chromosome-positive (Ph+) leukemia; arterial occlusive events (AOEs) occurred in ≥ 25% of patients based on investigator reporting. However, AOE rates vary depending on the definitions and reporting approach used. METHODS: To better understand clinically relevant AOEs with ponatinib, an independent cardiovascular adjudication committee reviewed 5-year AOE data from the PACE trial according to a charter-defined process and standardized event definitions. RESULTS: A total of 449 patients with chronic myeloid leukemia (CML) or Ph+ acute lymphoblastic leukemia (ALL) received ponatinib (median age 59 y; 47% female; 93% ≥ 2 prior tyrosine kinase inhibitors (TKIs); median follow-up, 37.3 months). The adjudicated AOE rate (17%) was lower than the non-adjudicated rate (i.e., rate before adjudication; 25%). The only adjudicated AOE in > 2% of patients was peripheral arterial occlusive disease (4%). Exposure-adjusted incidence of newly occurring adjudicated AOEs decreased over time. Patients with multiple baseline cardiovascular risk factors had higher adjudicated AOE rates than those without risk factors. CONCLUSIONS: This independent adjudication study identified lower AOE rates than previously reported, suggesting earlier overestimation that may inaccurately reflect AOE risk with ponatinib. This trial was registered under ClinicalTrials.gov identifier NCT01207440 on September 23, 2010 ( https://clinicaltrials.gov/ct2/show/NCT01207440 ).

Population Pharmacokinetics of Ponatinib in Healthy Adult Volunteers and Patients With Hematologic Malignancies and Model-Informed Dose Selection for Pediatric Development.

The BCR-ABL1 inhibitor ponatinib is approved for the treatment of adults with chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia, including those with the T315I mutation. We report a population pharmacokinetic model-based analysis for ponatinib and its application to inform dose selection for pediatric development. Plasma concentration-time data were collected from 260 participants (86 healthy volunteers; 174 patients with hematologic malignancies) enrolled across 7 clinical trials. Data were analyzed using nonlinear mixed-effects modeling. Ponatinib pharmacokinetics were described by a 2-compartment model with first-order elimination from the central compartment. The final model included body weight and age as covariates on the apparent central volume of distribution; however, exposure variability explained by these covariates was small compared with overall variability in the population. None of the covariates evaluated, including sex, age (19-85 years), race, body weight (40.7-152.0 kg), total bilirubin (0.1-3.16 mg/dL), alanine aminotransferase (6-188 U/L), albumin (23.0-52.5 g/L), and creatinine clearance (≥28 mL/min) had clinically meaningful effects on apparent oral clearance. Simulations based on the final model predicted that daily doses of 15 to 45 mg result in steady-state average concentrations that are in the pharmacological range for BCR-ABL1 inhibition and approximate or exceed concentrations associated with suppression of T315I mutant clones. The final model was adapted using allometric scaling to inform dose selection for pediatric development. Clinicaltrials.gov identifier: NCT00660920; NCT01667133; NCT01650805.

Ponatinib dose-ranging study in chronic-phase chronic myeloid leukemia: a randomized, open-label phase 2 clinical trial.

In PACE (Ponatinib Ph+ ALL and CML Evaluation), a phase 2 trial of ponatinib that included patients with chronic-phase chronic myeloid leukemia (CP-CML) resistant to multiple prior tyrosine kinase inhibitors (TKIs), ponatinib showed deep and durable responses, but arterial occlusive events (AOEs) emerged as notable adverse events. Post hoc analyses indicated that AOEs are dose dependent. We assessed the benefit/risk ratio across 3 ponatinib starting doses in the first prospective study to evaluate a novel, response-based, dose-reduction strategy for TKI treatment. Adults with CP-CML resistant to or intolerant of at least 2 prior BCR-ABL1 TKIs or with a BCR-ABL1 T315I mutation were randomly assigned 1:1:1 to 3 cohorts receiving ponatinib 45, 30, or 15 mg once daily. In patients who received 45 or 30 mg daily the dose was reduced to 15 mg upon response (BCR-ABL1IS transcript levels ≤1%). The primary end point was response at 12 months. From August 2015 through May 2019, 283 patients were randomly assigned to the cohorts: 282 (94 per dose group) received treatment (data cutoff, 31 May 2020). The primary end point (98.3% confidence interval) was achieved in 44.1% (31.7-57.0) in the 45-mg cohort, 29.0% (18.4-41.6) in the 30-mg cohort, and 23.1% (13.4-35.3) in the 15-mg cohort. Independently confirmed grade 3 or above treatment-emergent AOEs occurred in 5, 5, and 3 patients in the 45-, 30-, and 15-mg cohorts, respectively. All cohorts showed benefit in this highly resistant CP-CML population. Optimal benefit/risk outcomes occurred with the 45-mg starting dose, which was decreased to 15 mg upon achievement of a response. This trial is registered on www.clinicaltrials.gov as NCT02467270.

Comparison of incidence/occurrence of cardiovascular events between ponatinib vs bosutinib among patients with at least one prior line of tyrosine kinase inhibitors in chronic myeloid leukemia in a community setting in the United States.

INTRODUCTION: In this real-world study, the incidence of cardiovascular events (CV) including major adverse cardiac events (MACE), arterial occlusive events (AOE), and venous occlusive events (VOE) was evaluated in chronic myeloid leukemia (CML) patients treated with ponatinib or bosutinib in a US commercial database population. MATERIALS AND METHODS: CML patients aged ≥18 years with use of 1 or 2 prior tyrosine kinase inhibitors prescribed bosutinib or ponatinib were selected from the IBM® MarketScan® Research database. Cox proportional hazard model analyses were conducted to examine any difference in CV event risk. RESULTS: Ponatinib and bosutinib was associated with similar incidence and risk of CV events, including MACEs (HR: 1.02; 95% CI: 0.35, 3.01), AOEs (HR: 0.90; 95% CI: 0.43, 1.85) and VOEs (HR: 0.92; 95% CI: 0.44, 1.94). CONCLUSION: Treatment with ponatinib or bosutinib was not associated with significant differences in the incidence of CV events in CML patients.

SHP656, a polysialylated recombinant factor VIII (PSA-rFVIII): First-in-human study evaluating safety, tolerability and pharmacokinetics in patients with severe haemophilia A.

INTRODUCTION: SHP656 is the first factor VIII (FVIII) product developed using polysialylation (PSA) technology, in which full-length recombinant (r) FVIII (anti-haemophilic factor [recombinant]) is conjugated with a 20 kDa PSA polymer. AIM: To compare the safety, immunogenicity and pharmacokinetics of SHP656 vs the parent rFVIII (octocog alfa) after single infusions of 25-75 IU/kg in patients with severe haemophilia A (FVIII activity <1%). METHODS: Multinational, phase 1, prospective, open-label, two-period, fixed-sequence, dose-escalation trial (clinicaltrials.gov NCT02716194). Patients received single doses of rFVIII and then SHP656 sequentially at the same dose: 25 ± 3 IU/kg (Cohort 1), 50 ± 5 IU/kg (Cohort 2) and 75 ± 5 IU/kg (Cohort 3). RESULTS: Forty patients received rFVIII: 11 in Cohort 1, 16 in Cohort 2 and 13 in Cohort 3. Two patients withdrew before receiving SHP656, leaving 38 patients who completed the study and received both treatments. No treatment-related adverse events (AEs), serious AEs, deaths, study withdrawals, thrombotic events or allergic reactions were reported; and no significant treatment-related changes in laboratory parameters or vital signs. No patients developed FVIII inhibitors or antibodies to PSA. FVIII activity was significantly prolonged following SHP656 administration vs rFVIII with an approximately 1.5-fold extension in mean residence time (P < .05). Exposure increased proportional to the SHP656 dose over the 25-75 IU/kg dose range. CONCLUSION: Polysialylation of rFVIII confers a half-life extension similar to that of approved extended half-life products that use either PEGylation or Fc fusion technology and was not associated with any treatment-related adverse events.

Hydrophobic photolabeling studies identify the lipid-protein interface of the 5-HT3A receptor.

A HEK-293 cell line that stably expresses mouse 5-HT(3A)Rs containing a C-terminal extension that confers high-affinity binding of alpha-bungarotoxin (alphaBgTx) was established (alphaBgTx-5-HT(3A)Rs) and used to purify alphaBgTx-5-HT(3A)Rs in a lipid environment for use in structural studies using photoaffinity labeling. alphaBgTx-5-HT(3A)Rs were expressed robustly (60 pmol of [(3)H]BRL-43694 binding sites (approximately 3 microg of receptor) per milligram of protein) and displayed the same functional properties as wild-type receptors (serotonin EC(50) = 5.3 +/- 0.04 microM). While [(125)I]alphaBgTx bound to the alphaBgTx-5-HT(3A)Rs with high affinity (K(d) = 11 nM), application of nonradioactive alphaBgTx (up to 300 microM) had no effect on serotonin-induced current responses. alphaBgTx-5-HT(3A)Rs were purified on an alphaBgTx-derivatized affinity column from detergent extracts in milligram quantities and at approximately 25% purity. The hydrophobic photolabel 3-trifluoromethyl-3-(m-[(125)I]iodophenyl)diazirine ([(125)I]TID) was used to identify the amino acids at the lipid-protein interface of purified and lipid-reconstituted alphaBgTx-5-HT(3A)Rs. [(125)I]TID photoincorporation into the alphaBgTx-5-HT(3A)R subunit was initially mapped to subunit proteolytic fragments of 8 kDa, containing the M4 transmembrane segment and approximately 60% of incorporated (125)I, and 17 kDa, containing the M1-M3 transmembrane segments. Within the M4 segment, [(125)I]TID labeled Ser(451), equivalent to the [(125)I]TID-labeled residue Thr(422) at the lipid-exposed face of the Torpedo nicotinic acetylcholine receptor (nAChR) alpha1M4 alpha-helix. These results provide a first definition of the surface of the 5-HT(3A)R M4 helix that is exposed to lipid and establish that this surface is equivalent to the surface exposed to lipid in the Torpedo nAChR.

[(3)H]Epibatidine photolabels non-equivalent amino acids in the agonist binding site of Torpedo and alpha4beta2 nicotinic acetylcholine receptors.

Nicotinic acetylcholine receptor (nAChR) agonists, such as epibatidine and its molecular derivatives, are potential therapeutic agents for a variety of neurological disorders. In order to identify determinants for subtype-selective agonist binding, it is important to determine whether an agonist binds in a common orientation in different nAChR subtypes. To compare the mode of binding of epibatidine in a muscle and a neuronal nAChR, we photolabeled Torpedo alpha(2)betagammadelta and expressed human alpha4beta2 nAChRs with [(3)H]epibatidine and identified by Edman degradation the photolabeled amino acids. Irradiation at 254 nm resulted in photolabeling of alphaTyr(198) in agonist binding site Segment C of the principal (+) face in both alpha subunits and of gammaLeu(109) and gammaTyr(117) in Segment E of the complementary (-) face, with no labeling detected in the delta subunit. For affinity-purified alpha4beta2 nAChRs, [(3)H]epibatidine photolabeled alpha4Tyr(195) (equivalent to Torpedo alphaTyr(190)) in Segment C as well as beta2Val(111) and beta2Ser(113) in Segment E (equivalent to Torpedo gammaLeu(109) and gammaTyr(111), respectively). Consideration of the location of the photolabeled amino acids in homology models of the nAChRs based upon the acetylcholine-binding protein structure and the results of ligand docking simulations suggests that epibatidine binds in a single preferred orientation within the alpha-gamma transmitter binding site, whereas it binds in two distinct orientations in the alpha4beta2 nAChR.

Photoaffinity labeling the agonist binding domain of alpha4beta4 and alpha4beta2 neuronal nicotinic acetylcholine receptors with [(125)I]epibatidine and 5[(125)I]A-85380.

The development of nicotinic acetylcholine receptor (nAChR) agonists, particularly those that discriminate between neuronal nAChR subtypes, holds promise as potential therapeutic agents for many neurological diseases and disorders. To this end, we photoaffinity labeled human alpha4beta2 and rat alpha4beta4 nAChRs affinity-purified from stably transfected HEK-293 cells, with the agonists [(125)I]epibatidine and 5[(125)I]A-85380. Our results show that both agonists photoincorporated into the beta4 subunit with little or no labeling of the beta2 and alpha4 subunits respectively. [(125)I]epibatidine labeling in the beta4 subunit was mapped to two overlapping proteolytic fragments that begin at beta4V102 and contain Loop E (beta4I109-P120) of the agonist binding site. We were unable to identify labeled amino acid(s) in Loop E by protein sequencing, but we were able to demonstrate that beta4Q117 in Loop E is the principal site of [(125)I]epibatidine labeling. This was accomplished by substituting residues in the beta2 subunit with the beta4 homologs and finding [(125)I]epibatidine labeling in beta4 and beta2F119Q subunits with little, if any, labeling in alpha4, beta2, or beta2S113R subunits. Finally, functional studies established that the beta2F119/beta4Q117 position is an important determinant of the receptor subtype-selectivity of the agonist 5I-A-85380, affecting both binding affinity and channel activation.