Diversity in Clinical Pharmacology: A Call to Action

Prioritization of diversity, equity, and inclusion in all facets of our work is long overdue for the clinical pharmacology community. Increasing diversity in clinical research will deepen our understanding of nuanced patient populations and help improve all patient outcomes. Fostering an inclusive and diverse workforce will lead to broader perspectives that can better inform critical decisions and create work environments where everyone can thrive. In this call to action, we invite you to join us.

A Phase I, Open-Label, Dose-Finding Study of GSK2636771, a PI3Kβ inhibitor, Administered with Enzalutamide in Patients with Metastatic Castration-Resistant Prostate Cancer

PURPOSE

In patients with metastatic castration-resistant prostate cancer (mCRPC), resistance to androgen receptor (AR) targeted therapies, such as enzalutamide, remains an issue. Inactivation of inhibitory phosphatase and tensin homolog (PTEN) activates phosphoinositide 3-kinase (PI3K)/AKT signaling and contributes to resistance to androgen-deprivation therapy and poor outcomes. Therefore, dual targeting of AR and PI3K/AKT pathways may limit tumor growth and reverse resistance.

PATIENTS AND METHODS

In this Phase I study (NCT02215096), patients with PTEN-deficient mCRPC, who progressed on prior enzalutamide, received once-daily enzalutamide 160 mg plus PI3Kβ inhibitor GSK2636771 at 300 mg initial dose, with escalation or de-escalation in 100 mg increments, followed by dose expansion. Primary objectives were to evaluate safety/tolerability, determine the recommended Phase II dose (RP2D), and assess the 12-week non-progressive disease (PD) rate.

RESULTS

Overall, 37 patients were enrolled; 36 received {greater than or equal to}1 dose of GSK2636771 (200 mg: n=22, 300 mg: n=12; 400 mg: n=2) plus 160 mg enzalutamide. Dose-limiting toxicities occurred in 5 patients (200 mg: n=1; 300 mg: n=2, 400 mg: n=2). No new or unexpected adverse events nor evidence of drug-drug interaction were observed. At the recommended dose of GSK2636771 (200 mg) plus enzalutamide, the 12-week non-PD rate was 50% (95% CI: 28.2-71.8%, n=22); 1 (3%) patient achieved a radiographic partial response lasting 36 weeks. 4/34 (12%) patients had prostate-specific antigen reduction of {greater than or equal to}50%.

CONCLUSIONS

Although there was acceptable safety and tolerability with GSK2636771 plus enzalutamide in patients with PTEN-deficient mCRPC after failing enzalutamide, limited antitumor activity was observed.

Beneficial Pharmacokinetic Interaction Between Atazanavir and Lopinavir/Ritonavir

BACKGROUND

The combination of lopinavir/ritonavir (LPV/r) and atazanavir (ATV) with nucleoside reverse transcriptase inhibitors has been used as a salvage regimen in HIV-infected patients. Because these agents, to various degrees, are substrates, inducers, and inhibitors of CYP450 3A4, there is concern for alterations in the pharmacokinetics (PK) of these combined agents.

OBJECTIVE

To determine the steady-state PK interactions between ATV, ritonavir (RTV), and LPV when coadministered at various doses.

METHODS

HIV-negative subjects (n = 15) received a combination of ATV, RTV, and LPV in the following sequence: period I (days 1-10), ATV/r at a dose of 300/100 mg once daily; period II (days 11-24), ATV at a dose of 300 mg once daily plus LPV/r at a dose of 400/100 mg twice daily; and period III (days 25-34), ATV/r at a dose of 300/100 mg once daily plus LPV/r at a dose of 400/100 mg twice daily. Intensive PK analysis was performed on days 10, 24, and 34. A paired t test was used for pairwise comparison of log-transformed PK parameters of ATV and LPV.

RESULTS

In period II, the ATV minimum concentration (Cmin) geometric mean (GM) was higher compared with period I (GM: 0.75 vs. 0.51 microg/mL, geometric mean ratio (GMR) = 1.45, 90% confidence interval [CI]: 1.19 to 1.77; P = 0.006). The ATV area under the concentration-time curve from dosing to 24 hours after the dose (AUC0-24; GM: 36.40 vs. 39.62 microg.h/mL, GMR = 0.92, 90% CI: 0.80 to 1.05; P = 0.28) did not differ, however. The addition of 100 mg of RTV in period III did not significantly increase the ATV Cmin (GM: 0.84 vs. 0.75 microg/mL, GMR = 1.13, 90% CI: 0.91 to 1.40; P = 0.34) or ATV AUC0-24 (GM: 39.59 vs. 36.40 microg.h/mL, GMR = 1.09, 90% CI: 0.99 to 1.20; P = 0.14) compared with period II. The additional RTV in period III resulted in a higher LPV Cmin (GM: 5.12 vs. 3.99 microg/mL, GMR = 1.28, 90% CI: 1.15 to 1.43; P = 0.001), but the LPV areas under the concentration-time curve from dosing to 12 hours after the dose and maximum concentration were not significantly different. LPV PK parameters in period II were comparable to those of historical control subjects receiving LPV/r at a dose of 400/100 mg twice daily. All studied regimens were well tolerated. Indirect hyperbilirubinemia was the only grade 3 and 4 abnormality reported, which was expected given that ATV competitively inhibits UGTIA1 and has not been shown to result in other hepatic abnormalities.

CONCLUSIONS

The combination of ATV at a dose of 300 mg once daily plus LPV/r at a dose of 400/100 mg twice daily resulted in an appropriate PK profile for ATV and LPV and could be further evaluated in treatment-experienced patients requiring a dual-boosted protease inhibitor-containing regimen.