Estimation of Kidney Function in Patients With Multiple Myeloma: Implications for Lenalidomide Dosing.

BACKGROUND: Lenalidomide is an immunomodulatory drug used to treat multiple myeloma that requires renal dosing adjustment based on Cockcroft-Gault (CG). Various equations to estimate kidney function exist and pose a potential issue with lenalidomide dosing. OBJECTIVE: The objective of this analysis was to evaluate the impact of estimating kidney function in newly diagnosed multiple myeloma patients with CG, Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and their potential impact on lenalidomide dosing. METHODS: Data from 1121 multiple myeloma patients at the time of diagnosis acquired from the Mayo Clinic were used to calculate creatinine clearance (CrCl) using Cockcroft-Gault with actual body weight (CGABW), ideal body weight (CGIBW), or adjusted body weight (CGAdjBW); MDRD; and CKD-EPI for each subject. Discordances in dosing were then analyzed, and lenalidomide exposure was calculated for each subject to assess impact on pharmacokinetics of lenalidomide for patients who received discordant doses. RESULTS: Overall, approximately 16% of patients received a discordant dose when using MDRD or CKD-EPI instead of CGABW. The most common dose discordance was the decrease of a full dose of lenalidomide 25 mg when using CGABW down to 10 mg and when using MDRD or CKD-EPI with 53.8% to 55.6% of all discordances in this category. When assessing different body weights, the most common discordance was a decrease from 25 to 10 mg when using CGIBW instead of CGABW; the same trend was observed when using CGAdjBW instead as well. Patients were also at risk of over- or underexposure based on area under the concentration versus time curve (AUC) for discordant dosing. CONCLUSION AND RELEVANCE: A significant proportion of patients are at risk of under- or overdose of lenalidomide if CKD-EPI or MDRD are used instead of CGABW. Physicians should use CGABW when estimating renal function to dose lenalidomide.

Brief Report: Pharmacokinetics of Bictegravir and Tenofovir in Combination With Darunavir/Cobicistat in Treatment-Experienced Persons With HIV.

BACKGROUND: Bictegravir coformulated with emtricitabine and tenofovir alafenamide as a fixed-dose combination (BIC/FTC/TAF 50/200/25 mg) is recommended as an initial regimen in patients who are antiretroviral (ARV)-naïve or virologically suppressed on a stable ARV regimen. However, no real-world pharmacokinetic (PK) data are available in treatment-experienced patients with antiretroviral resistance receiving BIC/FTC/TAF plus a boosted protease inhibitor. SETTING/METHODS: This prospective, single-center, nonrandomized pharmacokinetic study enrolled adult treatment-experienced persons with HIV and creatinine clearance >30 mL/min receiving BIC/FTC/TAF + DRV/c as part of routine clinical care. Steady-state PK profiles of BIC, TAF, tenofovir (TFV), and DRV after daily dosing of BIC/FTC/TAF + darunavir/cobicistat (DRV/c) were obtained with samples at predose and 0.5, 1, 2, and 4 hours postdose. The AUC0-24 at steady state was extrapolated by imputing C0 for C24 for each participant (AUC0-tau,exp). RESULTS: Nine participants were enrolled with a median age of 59 years (range 54-67) and median number of years on ART of 19 (range 5.8-30). The median (interquartile range [IQR]) BIC AUC0-tau,exp and Cmax values were 128.9 µg*h/mL (78.1-159.5) and 6.9 µg/mL (5.1-9.8), respectively. The median (IQR) TAF AUC0-tau,exp and Cmax values were 0.376 µg*h/mL (0.199-0.430) and 0.276 µg/mL (0.149-0.543), respectively. Predose concentrations of TFV and DRV were comparable with historical data. CONCLUSION: Treatment-experienced persons with HIV receiving BIC/FTC/TAF + darunavir/cobicistat (DRV/c) had BIC exposures (AUC0-tau) that were increased by approximately 26% compared with historical PK data. Although TAF exposures were substantially increased, plasma TFV was only modestly higher. These results suggest that BIC/TAF/FTC + DRV/c is a viable antiviral regimen option for treatment-experienced persons.

Lopinavir and tenofovir interaction observed in non-pregnant adults altered during pregnancy.

WHAT IS KNOWN AND OBJECTIVE: Tenofovir exposure is increased in non-pregnant adults when tenofovir disoproxil fumarate is coadministered with lopinavir/ritonavir. In pregnant women, tenofovir exposure is decreased. Our objective is to describe the effect of lopinavir/ritonavir on tenofovir pharmacokinetics during pregnancy. METHODS: Data were collected through the International Maternal Pediatric and Adolescent AIDS Clinical Trials (IMPAACT) Network P1026s protocol. This was a nonrandomized, open-label, parallel-group and multicentre phase-IV prospective study in pregnant women with HIV. Intensive steady-state 24-h pharmacokinetic profiles were collected during the third trimester of pregnancy and postpartum. Tenofovir was measured in plasma using validated liquid chromatography-mass spectrometry method (quantification limit: 10 ng/ml). Statistical tests compared paired and between group pharmacokinetic data. RESULTS AND DISCUSSION: In women not receiving lopinavir/ritonavir (n = 28), tenofovir AUC0-24 was 27% lower (2.2 mcg·h/ml vs 2.8 mcg·h/ml, p = 0.002) and oral clearance was 27% higher (61 L/h vs 48 L/h, p = 0.001) during the third trimester compared to paired postpartum data. In women receiving lopinavir/ritonavir (n = 10), tenofovir AUC0-24 and oral clearance were not different antepartum compared to postpartum. Women with and women without concomitant lopinavir/ritonavir displayed no significant differences in postpartum tenofovir pharmacokinetics. WHAT IS NEW AND CONCLUSION: Tenofovir exposure during the third trimester was reduced compared to postpartum in pregnant women not receiving lopinavir/ritonavir, but not in pregnant women also receiving lopinavir/ritonavir. Our findings suggest that pregnancy confounds the expected decrease in tenofovir exposure with concomitant lopinavir/ritonavir in non-pregnant adults. These findings illustrate the need for drug-drug interaction studies in pregnant women as drug disposition differs significantly in pregnant women compared to non-pregnant adults.

Discordance Between Child-Pugh and National Cancer Institute Classifications for Hepatic Dysfunction: Implications on Dosing Recommendations for Oncology Compounds.

Guidance from the U.S. Food and Drug Administration (FDA) and the European Medicines Agency recommends using Child-Pugh classification for pharmacokinetic evaluation in noncancer subjects with hepatic impairment (HI). Therefore, dosing recommendations for oncology compounds for patients with HI are commonly based on Child-Pugh classification. In oncology clinical practice, National Cancer Institute classification (NCIc), is commonly used for evaluating hepatic function and dosing decisions for oncology patients. This work evaluated the discordance between the 2 systems and the impact on dosing recommendations. The classification system in HI studies was reviewed for FDA-approved oncology compounds. Discordance between Child-Pugh and NCIc was evaluated for sunitinib, dacomitinib, palbociclib, bosutinib, and axitinib. Pharmacokinetic (PK) analyses were conducted based on Child-Pugh classification and NCIc. Review of 117 approved oncology compounds showed prevalent use of Child-Pugh classification for dedicated HI studies in noncancer subjects. NCIc is commonly used in cancer patient studies. NCIc tended to classify subjects as less impaired versus Child-Pugh (64.9%, 73.7%, and 61.5% of subjects with mild, moderate, and severe HI, respectively, via Child-Pugh were classified as at least 1 category less impaired via NCIc). PK analyses by NCIc were consistent with Child-Pugh for sunitinib, dacomitinib, and palbociclib. For bosutinib, NCIc showed less impact of HI than Child-Pugh; an opposite trend was observed for axitinib. The impact of this considerable discordance between the 2 systems on dosing decisions bears consideration. When Child-Pugh is used for HI study enrollment, exploratory PK analyses based on NCIc should be conducted. Prescribers should attempt to use the same classification system in the product label for dosing decisions.

Pharmacokinetic Enhancement of HIV Antiretroviral Therapy During Pregnancy.

Pharmacokinetic boosting of antiretroviral (ARV) therapies with either ritonavir or cobicistat is used to achieve target drug exposure, lower pill burden, and provide simplified dosing schedules. Several ARVs require boosting, including the integrase inhibitor elvitegravir as well as protease inhibitors such as darunavir, atazanavir, and lopinavir. The use of boosted regimens in pregnant women living with HIV has been studied for a variety of ARVs; however, a recent recommendation by the US Food and Drug Administration advised against cobicistat-boosted regimens in pregnancy due to substantially lower drug exposures observed in clinical pharmacokinetic studies. The objectives of this article are to review pharmacokinetic enhancement of ARVs with ritonavir and cobicistat during pregnancy and postpartum, describe clinical implications, and provide recommendations for future research.