ABSTRACT
Background: Bemnifosbuvir (BEM, AT-527) is a guanosine nucleotide prodrug candidate for the treatment of COVID-19 and chronic HCV. BEM was identified in vitro as an inhibitor of drug transporters P-glycoprotein, breast cancer resistant protein (BCRP) and organic anion transporting polypeptide 1B1 (OATP1B1). Ph 1 studies in healthy participants were conducted to assess the clinical implications of these results using digoxin (DIG) and rosuvastatin (ROSU) as P-gp and BCRP/ OATP1B1 index drugs, respectively. Method(s): Both studies employed a similar design with 2 groups of 14 healthy participants: Day 1/period 1, all participants received a single dose of DIG 0.25mg or ROSU 10mg alone. In period 2, participants received DIG 0.25mg or ROSU 10mg with BEM 1100mg, simultaneously (n=14) or staggered by 2h (n=14). Serial plasma samples were collected and quantitated for DIG or ROSU concentrations. Result(s): A single dose of BEM 1100mg simultaneously administered slightly increased the Cmax of DIG (78%), yet had no effect on its AUC, consistent with the transient nature of BEM plasma PK. When dosed staggered, BEM did not affect the PK of DIG. A single dose (simultaneous or staggered) of BEM 1100mg slightly increased the plasma exposure of ROSU (20%-40%). There was no effect on vital signs, ECG, and no SAEs or drug discontinuations. Conclusion(s): A single high dose of BEM 1100mg only slightly increased the plasma exposure of the P-gp and BCRP/OATP1B1 index drugs DIG and ROSU. BEM has low potential to exhibit clinical meaningful inhibition of these transporters. No dose adjustment will be needed for drugs that are sensitive substrates of P-gp or BCRP/OAT1B1 when co-administered with BEM, staggered dosing may lessen any DDI risk.
ABSTRACT
Effective drug delivery to the brain is critical for the treatment of glioblastoma (GBM), an aggressive and invasive primary brain tumor that has a dismal prognosis. Radiation therapy, the mainstay of brain tumor treatment, works by inducing DNA damage. Therefore, inhibiting DNA damage response (DDR) pathways can sensitize tumor cells to radiation and enhance cytotoxicity. AZD1390 is an inhibitor of ataxia-telangiectasia mutated kinase, a critical regulator of DDR. Our in vivo studies in the mouse indicate that delivery of AZD1390 to the central nervous system (CNS) is restricted due to active efflux by P-glycoprotein (P-gp). The free fraction of AZD1390 in brain and spinal cord were found to be low, thereby reducing the partitioning of free drug to these organs. Coadministration of an efflux inhibitor significantly increased CNS exposure of AZD1390. No differences were observed in distribution of AZD1390 within different anatomic regions of CNS, and the functional activity of P-gp and breast cancer resistance protein also remained the same across brain regions. In an intracranial GBM patient-derived xenograft model, AZD1390 accumulation was higher in the tumor core and rim compared with surrounding brain. Despite this heterogenous delivery within tumor-bearing brain, AZD1390 concentrations in normal brain, tumor rim, and tumor core were above in vitro effective radiosensitizing concentrations. These results indicate that despite being a substrate of efflux in the mouse brain, sufficient AZD1390 exposure is anticipated even in regions of normal brain. SIGNIFICANCE STATEMENT Given the invasive nature of glioblastoma (GBM), tumor cells are often protected by an intact blood-brain barrier, requiring the development of brain-penetrant molecules for effective treatment. We show that efflux mediated by P-glycoprotein (P-gp) limits central nervous system (CNS) distribution of AZD1390 and that there are no distributional differences within anatomical regions of CNS. Despite efflux by P-gp, concentrations effective for potent radiosensitization are achieved in GBM tumor-bearing mouse brains, indicating that AZD1390 is an attractive molecule for clinical development of brain tumors.Copyright © 2022 American Society for Pharmacology and Experimental Therapy. All rights reserved.