Exposure-Response Analyses of Letermovir Following Oral and Intravenous Administration in Allogeneic Hematopoietic Cell Transplantation Recipients.

The cytomegalovirus (CMV) viral terminase inhibitor letermovir is approved for prophylaxis of CMV infection and disease in adult CMV-seropositive allogeneic hematopoietic stem cell transplantation recipients. In a phase III trial (NCT02137772), letermovir significantly reduced clinically significant CMV infection (CS-CMVi) rate vs. placebo through Week 24 (primary end point) and Week 14 (secondary end point) post transplantation. Here, exposure-response relationships were investigated using efficacy and selected safety end points from the phase III trial to inform the proposed clinical dose. Post hoc exposure estimates were derived from a population pharmacokinetic model. No significant exposure dependencies were found for CS-CMVi through Week 24 or Week 14 among letermovir-treated participants. Evaluated covariates had no impact on exposure-efficacy relationships and letermovir plasma exposure did not affect time of CS-CMVi onset. There was no dependence between adverse event incidence and letermovir exposure. These results support current dosing recommendations in several countries and regions, including the United States and European Union.

Population Pharmacokinetics, Exposure-Response, and Probability of Target Attainment Analyses for Tedizolid in Adolescent Patients with Acute Bacterial Skin and Skin Structure Infections.

Tedizolid phosphate is an oxazolidinone antibacterial agent approved for the treatment of Gram-positive acute bacterial skin and skin structure infections (ABSSSIs) in patients aged ≥12 years. To support the use of tedizolid phosphate in adolescents with ABSSSIs, a population pharmacokinetic (PK) model, developed using adult and pediatric data, was updated to include PK data from a phase 3 clinical trial (PN012) that evaluated the safety and efficacy of once-daily oral or intravenous 200-mg tedizolid phosphate treatment in adolescents (12 to <18 years) with ABSSSIs, along with emerging data from a phase 1 trial (PN013) in children (2 to <12 years). Updated PK parameter estimates remained similar to those of the previous model. Body weight was a statistically significant covariate on clearance and volume parameters, with no clinically meaningful effects on exposure in adolescents. Tedizolid exposures in adolescents from PN012 were slightly higher with largely overlapped area under the concentration-time curve distribution compared with adults from previous phase 2 and 3 trials. The probability of PK/pharmacodynamic target attainment at the MIC susceptibility breakpoint of 0.5 µg/ml for Staphylococcus and Streptococcus sp. was 100%. As most participants from the PN012 trial were cured, no significant exposure-efficacy relationship was identified. Tedizolid exposures were similar between participants with and without a safety event from PN012; no clear relationship was detected between exposure and safety. Despite lower body weight and higher exposures in adolescents, safety profiles in adolescents were similar those in adults. These results support the 200-mg, once-daily intravenous or oral dose of tedizolid phosphate in adolescents with ABSSSIs.

Pharmacokinetics and Safety of Single-dose Tedizolid Phosphate in Children 2 to <12 Years of Age.

BACKGROUND: Infections with Gram-positive bacteria, including acute bacterial skin and skin structure infections (ABSSSIs), are common in children. We describe a single-dose pharmacokinetics and safety study of tedizolid phosphate, a new oxazolidinone under investigation for the treatment of ABSSSIs in children, in hospitalized participants 2 to <12 years of age. METHODS: This open-label, multicenter, phase 1 trial (NCT02750761) enrolled hospitalized children 2 to <12 years of age receiving treatment for a confirmed/suspected Gram-positive bacterial infection. Participants were stratified by age (2 to <6 years and 6 to <12 years) to receive a single oral or intravenous dose of tedizolid phosphate. Evaluations included safety and pharmacokinetics of tedizolid phosphate and its active metabolite, tedizolid. Palatability of the oral suspension was also evaluated. RESULTS: Thirty-two participants were enrolled and received 3-6 mg/kg of study medication. For both routes of administration, tedizolid phosphate was rapidly converted to tedizolid; median time to maximum tedizolid plasma concentration was 1-2 hours after initiation of the 1-hour intravenous infusion and 2-3 hours after oral dosing. The tedizolid mean terminal half-life was 5-6 hours and 6-7 hours for the intravenous and oral administration groups, respectively. The oral tedizolid phosphate suspension demonstrated high bioavailability comparable to that of the parenteral administration. A single dose of intravenous or oral tedizolid phosphate was well tolerated; no unexpected safety findings were observed. CONCLUSIONS: Pharmacokinetic and safety observations provide the information necessary for the continued development of tedizolid phosphate for the treatment of Gram-positive infections in children, particularly ABSSSIs.

Population pharmacokinetics of letermovir following oral and intravenous administration in healthy participants and allogeneic hematopoietic cell transplantation recipients.

Letermovir is indicated for prophylaxis of cytomegalovirus infection and disease in allogeneic hematopoietic stem cell transplant (HSCT) recipients. Two-stage population pharmacokinetic (PK) modeling of letermovir was conducted to support dose rationale and evaluate the impact of intrinsic/extrinsic factors. Data from healthy phase I study participants over a wide dose range were modeled to evaluate the effects of selected intrinsic factors, including pharmacogenomics; next, phase III HSCT-recipient data at steady-state following clinical doses were modeled. The model in HSCT recipients adequately described letermovir PK following both oral or i.v. administration, and was consistent with the healthy participant model at steady-state clinical doses. Intrinsic factor effects were not clinically meaningful. These staged analyses indicate that letermovir PK in HSCT recipients and healthy participants differ only with respect to bioavailability and absorption rate. The HSCT recipient model was suitable for predicting exposure for exposure-response analysis supporting final dose selection.

Pharmacokinetics and Pharmacological Properties of Chloroquine and Hydroxychloroquine in the Context of COVID-19 Infection.

Chloroquine and hydroxychloroquine are quinoline derivatives used to treat malaria. To date, these medications are not approved for the treatment of viral infections, and there are no well-controlled, prospective, randomized clinical studies or evidence to support their use in patients with coronavirus disease 2019 (COVID-19). Nevertheless, chloroquine and hydroxychloroquine are being studied alone or in combination with other agents to assess their effectiveness in the treatment or prophylaxis for COVID-19. The effective use of any medication involves an understanding of its pharmacokinetics, safety, and mechanism of action. This work provides basic clinical pharmacology information relevant for planning and initiating COVID-19 clinical studies with chloroquine or hydroxychloroquine, summarizes safety data from healthy volunteer studies, and summarizes safety data from phase II and phase II/III clinical studies in patients with uncomplicated malaria, including a phase II/III study in pediatric patients following administration of azithromycin and chloroquine in combination. In addition, this work presents data describing the proposed mechanisms of action against the severe acute respiratory distress syndrome coronavirus-2 and summarizes clinical efficacy to date.

Erratum: Disruption of Myc-Max Heterodimerization with Improved Cell-Penetrating Analogs of the Small Molecule 10074-G5.

[This corrects the article DOI: 10.18632/oncotarget.1108.].

Sorafenib Dose Recommendation in Acute Myeloid Leukemia Based on Exposure-FLT3 Relationship.

Sorafenib administered at the approved dose continuously is not tolerated long-term in patients with acute myeloid leukemia (AML). The purpose of this study was to optimize the dosing regimen by characterizing the sorafenib exposure-response relationship in patients with AML. A one-compartment model with a transit absorption compartment and enterohepatic recirculation described the exposure. The relationship between sorafenib exposure and target modulation of kinase targets (FMS-like tyrosine kinase 3 (FLT3)-ITD and extracellular signal-regulated kinase (ERK)) were described by an inhibitory maximum effect (Emax ) model. Sorafenib could inhibit FLT3-ITD activity by 100% with an IC50 of 69.3 ng/mL and ERK activity by 84% with an IC50 of 85.7 ng/mL (both adjusted for metabolite potency). Different dosing regimens utilizing 200 or 400 mg at varying frequencies were simulated based on the exposure-response relationship. Simulations demonstrate that a 200 mg twice daily (b.i.d.) dosing regimen showed similar FLT3-ITD and ERK inhibitory activity compared with 400 mg b.i.d. and is recommended in further clinical trials in patients with AML.

Discovery of methyl 4'-methyl-5-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)-[1,1'-biphenyl]-3-carboxylate, an improved small-molecule inhibitor of c-Myc-max dimerization.

c-Myc is a basic helix-loop-helix-leucine zipper (bHLH-ZIP) transcription factor that is responsible for the transcription of a wide range of target genes involved in many cancer-related cellular processes. Over-expression of c-Myc has been observed in, and directly contributes to, a variety of human cancers including those of the hematopoietic system, lung, prostate and colon. To become transcriptionally active, c-Myc must first dimerize with Myc-associated factor X (Max) via its own bHLH-ZIP domain. A proven strategy towards the inhibition of c-Myc oncogenic activity is to interfere with the structural integrity of the c-Myc-Max heterodimer. The small molecule 10074-G5 is an inhibitor of c-Myc-Max dimerization (IC50 =146 µM) that operates by binding and stabilizing c-Myc in its monomeric form. We have identified a congener of 10074-G5, termed 3jc48-3 (methyl 4'-methyl-5-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)-[1,1'-biphenyl]-3-carboxylate), that is about five times as potent (IC50 =34 µM) at inhibiting c-Myc-Max dimerization as the parent compound. 3jc48-3 exhibited an approximate twofold selectivity for c-Myc-Max heterodimers over Max-Max homodimers, suggesting that its mode of action is through binding c-Myc. 3jc48-3 inhibited the proliferation of c-Myc-over-expressing HL60 and Daudi cells with single-digit micromolar IC50 values by causing growth arrest at the G0 /G1 phase. Co-immunoprecipitation studies indicated that 3jc48-3 inhibits c-Myc-Max dimerization in cells, which was further substantiated by the specific silencing of a c-Myc-driven luciferase reporter gene. Finally, 3jc48-3's intracellular half-life was >17 h. Collectively, these data demonstrate 3jc48-3 to be one of the most potent, cellularly active and stable c-Myc inhibitors reported to date.

Disruption of Myc-Max heterodimerization with improved cell-penetrating analogs of the small molecule 10074-G5.

The c-Myc (Myc) oncoprotein is a high-value therapeutic target given that it is deregulated in multiple types of cancer. However, potent small molecule inhibitors of Myc have been difficult to identify, particularly those whose mechanism relies on blocking the association between Myc and its obligate heterodimerization partner, Max. We have recently reported a structure-activity relationship study of one such small molecule, 10074-G5, and generated an analog, JY-3-094, with significantly improved ability to prevent or disrupt the association between recombinant Myc and Max proteins. However, JY-3094 penetrates cells poorly. Here, we show that esterification of a critical para-carboxylic acid function of JY-3-094 by various blocking groups significantly improves cellular uptake although it impairs the ability to disrupt Myc-Max association in vitro. These pro-drugs are highly concentrated within cells where JY-3-094 is then generated by the action of esterases. However, the pro-drugs are also variably susceptible to extracellular esterases, which can deplete extracellular reservoirs. Furthermore, while JY-3-094 is retained by cells for long periods of time, much of it is compartmentalized within the cytoplasm in a form that appears to be less available to interact with Myc. Our results suggest that persistently high extracellular levels of pro-drug, without excessive susceptibility to extracellular esterases, are critical to establishing and maintaining intracellular levels of JY-3-094 that are sufficient to provide for long-term inhibition of Myc-Max association. Analogs of JY-3-094 appear to represent promising small molecule Myc inhibitors that warrant further optimization.