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Bictegravir (BIC) is a potent small-molecule integrase strand-transfer inhibitor (INSTI) and a component of Biktarvy®, a single-tablet combination regimen that is currently approved for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. The in vitro properties, pharmacokinetics (PK), and drug-drug interaction (DDI) profile of BIC were characterised in vitro and in vivo.BIC is a weakly acidic, ionisable, lipophilic, highly plasma protein-bound BCS class 2 molecule, which makes it difficult to predict human PK using standard methods. Its systemic plasma clearance is low, and the volume of distribution is approximately the volume of extracellular water in nonclinical species. BIC metabolism is predominantly mediated by cytochrome P450 enzyme (CYP) 3A and UDP-glucuronosyltransferase 1A1. BIC shows a low potential to perpetrate clinically meaningful DDIs via known drug metabolising enzymes or transporters.The human PK of BIC was predicted using a combination of bioavailability and volume of distribution scaled from nonclinical species and a modified in vitro-in vivo correlation (IVIVC) correction for clearance. Phase 1 studies in healthy subjects largely bore out the prediction and supported the methods used. The approach presented herein could be useful for other drug molecules where standard projections are not sufficiently accurate. Bictegravir (BIC) is a potent small-molecule integrase strand-transfer inhibitor (INSTI) and a component of Biktarvy®, a single-tablet combination regimen that is currently approved for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. The in vitro properties, pharmacokinetics (PK), and drug-drug interaction (DDI) profile of BIC were characterised in vitro and in vivo. BIC is a weakly acidic, ionisable, lipophilic, highly plasma protein-bound BCS class 2 molecule, which makes it difficult to predict human PK using standard methods. Its systemic plasma clearance is low, and the volume of distribution is approximately the volume of extracellular water in nonclinical species. BIC metabolism is predominantly mediated by cytochrome P450 enzyme (CYP) 3A and UDP-glucuronosyltransferase 1A1. BIC shows a low potential to perpetrate clinically meaningful DDIs via known drug metabolising enzymes or transporters. The human PK of BIC was predicted using a combination of bioavailability and volume of distribution scaled from nonclinical species and a modified in vitro-in vivo correlation (IVIVC) correction for clearance. Phase 1 studies in healthy subjects largely bore out the prediction and supported the methods used. The approach presented herein could be useful for other drug molecules where standard projections are not sufficiently accurate.

4130 Background: Glucocorticoid receptor (GR) pathway activation has been linked with chemotherapy resistance (CTR). RELA (formerly CORT125134, Corcept Therapeutics), a potent selective GR modulator, in combination with paclitaxel reduced CTR and enhanced activity against tumor growth in preclinical models of solid tumors. Methods: Patients (pts) with advanced solid tumors, ≤3 prior lines of cytotoxic therapy, ECOG status 0-1, and adequate marrow function received RELA (100, 150, or 200mg) + NP (60, 80, or 100mg/m2). Once daily RELA was given either continuously (CON) or intermittently (INT) (day before, of, and after NP). NP was dosed weekly for 3 of 4 weeks (wks) of a 28-day cycle. Prior NP therapy was allowed. Results: 72 pts have been enrolled [mean age 60 (range 18-81), mean number of prior therapies 3, prior taxane (TXN) treatment 54/72 (75%)]. 61 pts received ≥1 dose of RELA. Grade ≥3 AE ≥10% for CON: neutropenia (6/43, 14%); INT: neutropenia (6/18, 33%), anemia (2/18, 11%), and mucosal inflammation (2/18, 11%). Prophylactic G-CSF became mandatory in later cohorts. Recommended Phase 2 Dose: RELA 100mg-CON/150mg-INT + NP 80mg/m2 (exposures similar to NP 100mg/m2 due to CYP3A4 inhibition by RELA). Disease control (DC) > 24 wks was noted in 5/27 (19%) PDAC pts: 3 PR, 2 SD (27-50 wks). 3 pts achieved benefit despite progression on prior TXN with time to progression (TTP) 1.9-3.6x longer than prior TXN. 4/13 (31%) OvCA pts had DC > 24 wks: 1 CR, 1 PR, 2 SD (33-54+ wks). 1 pt had TTP 4.4x longer than prior TXN. 3 additional PRs were observed: acinar pancreatic cancer, TTP 31 wks (4.4x prior TXN); vulvar SCC HPV+, TTP 55 wks (3.9x prior TXN); cholangiocarcinoma, DC 29+ wks. Expression of GR-regulated genes involved in inflammation, apoptosis, and CTR distinguished pts with DC from pts without DC, providing proof of mechanism. Conclusions: RELA+NP resulted in durable disease control in pts with metastatic PDAC, OvCA, and other solid tumors, including those that have progressed on prior TXN. TTP was often several-fold longer than previously achieved on TXN therapy. Toxicities are manageable with prophylaxis for neutropenia. Further evaluation in OvCA NCT03776812, PDAC, and others are planned. Clinical trial information: NCT02762981.

Background Tenofovir disoproxil fumarate can cause renal and bone toxic effects related to high plasma tenofovir concentrations. Tenofovir alafenamide is a novel tenofovir prodrug with a 90% reduction in plasma tenofovir concentrations. Tenofovir alafenamide-containing regimens can have improved renal and bone safety compared with tenofovir disoproxil fumarate-containing regimens. Methods In these two controlled, double-blind phase 3 studies, we recruited treatment-naive HIV-infected patients with an estimated creatinine clearance of 50 mL per min or higher from 178 outpatient centres in 16 countries. Patients were randomly assigned (1:1) to receive once-daily oral tablets containing 150 mg elvitegravir, 150 mg cobicistat, 200 mg emtricitabine, and 10 mg tenofovir alafenamide (E/C/F/tenofovir alafenamide) or 300 mg tenofovir disoproxil fumarate (E/C/F/tenofovir disoproxil fumarate) with matching placebo. Randomisation was done by a computer-generated allocation sequence (block size 4) and was stratified by HIV-1 RNA, CD4 count, and region (USA or ex-USA). Investigators, patients, study staff, and those assessing outcomes were masked to treatment group. All participants who received one dose of study drug were included in the primary intention-to-treat efficacy and safety analyses. The main outcomes were the proportion of patients with plasma HIV-1 RNA less than 50 copies per mL at week 48 as defined by the the US Food and Drug Adminstration (FDA) snapshot algorithm (pre-specified non-inferiority margin of 12%) and pre-specified renal and bone endpoints at 48 weeks. These studies are registered with ClinicalTrials.gov, numbers NCT01780506 and NCT01797445. Findings We recruited patients from Jan 22, 2013, to Nov 4, 2013 (2175 screened and 1744 randomly assigned), and gave treatment to 1733 patients (866 given E/C/F/tenofovir alafenamide and 867 given E/C/F/tenofovir disoproxil fumarate). E/C/F/tenofovir alafenamide was non-inferior to E/C/F/tenofovir disoproxil fumarate, with 800 (92%) of 866 patients in the tenofovir alafenamide group and 784 (90%) of 867 patients in the tenofovir disoproxil fumarate group having plasma HIV-1 RNA less than 50 copies per mL (adjusted difference 2·0%, 95% CI -0·7 to 4·7). Patients given E/C/F/tenofovir alafenamide had significantly smaller mean serum creatinine increases than those given E/C/F/tenofovir disoproxil fumarate (0·08 vs 0·12 mg/dL; p