The Effect of Oral Letermovir Administration on the Pharmacokinetics of a Single Oral Dose of P-Glycoprotein Substrate Digoxin in Healthy Volunteers.

Letermovir is a human cytomegalovirus (CMV) terminase inhibitor approved in the United States, Canada, Japan, and the European Union for prophylaxis of CMV infection and disease in CMV-seropositive, allogeneic, hematopoietic stem-cell transplant recipients. In vitro, letermovir is a substrate and potential modulator of P-glycoprotein. The potential of letermovir to alter the pharmacokinetics of digoxin (a P-glycoprotein substrate) upon coadministration in healthy subjects was therefore investigated in a phase 1 trial (EudraCT: 2011-004516-39). Oral letermovir 240 mg was administered twice daily for 12 days with a single oral digoxin 0.5-mg dose on day 7; after a washout period, oral digoxin 0.5 mg was administered on day 35 (sequence 1). The period order was reversed after a 28-day washout for sequence 2. Pharmacokinetics and safety were evaluated. The presence of steady-state letermovir reduced digoxin area under the plasma concentration-time curve from administration until last quantifiable measurement by 12% and maximum plasma concentration by 22% compared with digoxin alone; digoxin half-life and elimination rate remained similar in both conditions. The between-subject variability of digoxin maximum plasma concentration was higher with letermovir than without (42% vs 31%) and similar for digoxin area under the plasma concentration-time curve in both periods. No specific safety or tolerability concerns were identified. Overall, letermovir had no clinically relevant effect on concomitant administration with digoxin.

Pharmacokinetics and safety of letermovir, a novel anti-human cytomegalovirus drug, in patients with renal impairment.

AIMS: Human cytomegalovirus remains a significant issue for immunocompromised patients and existing viral polymerase targeting therapies are associated with significant toxicity. Accordingly, the viral terminase complex inhibitor, letermovir, is in development. We assessed letermovir pharmacokinetics in renal impairment. METHODS: This was a Phase 1, open-label, nonrandomised trial. Estimated glomerular filtration rate based on the Modification of Diet Renal Disease equation was used to create three groups of eight subjects: healthy function (estimated glomerular filtration rate ≥ 90 ml min-1  1.73m-2 ), moderate (30-59 ml min-1  1.73m-2 ) and severe (<30 ml min-1  1.73m-2 ) impairment. Oral letermovir 120 mg was dosed once-daily for 8 days and blood collected for pharmacokinetic analyses. RESULTS: All 24 subjects enrolled completed the trial. Moderate and severe renal impairment increased mean unbound letermovir fractions by 11% and 26%, respectively, vs. healthy subjects. Exposure (AUCτ,ss and Css,max ) was increased with renal impairment [least square mean ratios (90% confidence intervals) total letermovir vs. healthy subjects, AUCτ,ss 192% (143-258%) and 142% (83-243%) for moderate and severe impairment, respectively; Css,max 125% (87-182%) and 106% (75-151%), respectively]. Clearance was decreased vs. healthy subjects. Correlation analyses indicated a correlation between decreasing renal function and increased unbound letermovir concentration (R2  = 0.5076, P < 0.0001). Correlations were identified between decreased clearance with both decreased renal function (R2  = 0.0662, P = 0.2249 and R2  = 0.1861, P = 0.0353 total and unbound clearance, respectively) and increased age (R2  = 0.3548, P = 0.0021 and R2  = 0.3166, P = 0.0042 total and unbound clearance, respectively). Multiple-dose letermovir 120 mg was well tolerated across groups. CONCLUSIONS: Renal impairment increased exposure to letermovir, although age was a confounding factor.

Precision Medicine in Oncology and Immuno-Oncology: Where We Stand and Where We're Headed.

BACKGROUND/AIMS: Precision medicine has only been a clinical reality only since the start of the 21st century, spurred on by the coevolution of science and technologies, as well as the increasing medical needs of aging societies of industrialized countries. Its overarching objective, from the perspective of the pharmaceutical and diagnostic industry, is to develop innovative therapeutic "concepts" with increased value for patients in a global health economy context. This article analyzes the recent advances and remaining challenges from a research, medical, and regulatory perspective in the development and introduction of precision medicine in oncology, more precisely in immuno-oncology. METHODS: Analysis of the most recent scientific publications and clinical evidence. RESULTS AND CONCLUSION: Stakeholders need to combine efforts in order to turn scientific insights, such as those related to predictive biomarkers, into superior and affordable therapeutic concepts. Policymakers should also help to bring this about by ensuring that a suitable regulatory framework and incentive system are in place in order to encourage groundbreaking innovation, and hence the availability of new treatment options for patients.

Heterologous co-expression of human cytochrome P450 1A2 and polymorphic forms of N-acetyltransferase 2 for studies on aromatic amines in V79 Chinese hamster cells.

V79 Chinese hamster cells were genetically engineered for the stable co-expression of human cytochrome P450 1A2 and the polymorphic N-acetyltransferase 2 alleles *4, *5B, *6A and *13, in order to generate an in vitro tool for studying the metabolism-dependent toxicity of aromatic amines. N-acetyltransferase 2*4-encoding cDNA was generated by the polymerase chain reaction (PCR) with defined primers from the genomic DNA of a human liver donor homozygous for *4, and served as a template to generate the *5B, *6A and *13 isoforms by site-directed mutagenesis. Human cytochrome P450 (CYP) 1A2-encoding cDNA was generated by the PCR from genomic DNA of the recombinant V79MZh1A2 cell line. All the cDNAs were inserted into a CMV promoter-containing plasmid in conjunction with the selectable marker genes, neomycin and hydromycin. The recombinant expression plasmids were transfected for stable integration into the genomic DNA of the V79 cells. Several cellular clones were obtained and checked for the genomic integration of intact cDNAs with the PCR on the genomic DNA of the recombinant cells. Stable expression was confirmed by the reverse transcriptase PCR (RT-PCR) on RNA preparations. Metabolic function was tested with ethoxyresorufin as a marker substrate for CYP1A2, and 2-aminofluorene and N-sulphametazine for N-acetyltransferase activity, and compared to data obtained from biological samples. 7-Ethoxyresorufin-O-deethylase activities ranged from 0.2 to 4 pmol resorufin/min/mg total protein. The N-acetylation of sulphametazine ranged from 0.07 to 1.7 nmol N-acetyl-sulphametazine/mg total protein/min. Selected clones showing activities in the range of physiological activities were submitted to metabolism dependent mutagenicity studies. In particular, the polymorphism-dependent N-acetylation of 2-aminofluorene and the role of CYP1A2 and N-acetyltransferase in the mutagenicity of 2-aminofluorene, were investigated. Surprisingly, the mutagenicity of 2-aminofluorene is dramatically reduced in V79 cells co-expressing CYP1A2 and N-acetyltransferase, compared to V79 cells expressing CYP1A2 only, pointing to a significant species-dependent difference in the metabolic activation of aromatic amines between rats and humans.