Transcriptomic analysis of GITR and GITR ligand reveals cancer immune heterogeneity with implications for GITR targeting.

Glucocorticoid-induced tumor necrosis factor related protein (GITR) is a transmembrane protein expressed mostly on CD25+CD4+ regulatory T-cells (Tregs) and upregulated on all T-cells upon activation. It is a T-cell co-stimulatory receptor and has demonstrated promising anti-tumor activity in pre-clinical studies. To date, however, the efficacy of GITR agonism has been discouraging in clinical trials. This study explores GITR and GITR ligand (GITR-L) ribonucleic acid (RNA) expression in solid tumors in an attempt to delineate causes for variable responses to GITR agonists. RNA expression levels of 514 patients with a variety of cancer types were normalized to internal housekeeping gene profiles and ranked as percentiles. 99/514 patients (19.3%) had high GITR expression (defined as ≥ 75th percentile). Breast and lung cancer had the highest proportion of patients with high GITR expression (39% and 35%, respectively). The expression of concomitant high GITR and low-moderate GITR-L expression (defined as <75th percentile) was present in 31% and 30% of patients with breast and lung cancer respectively. High GITR expression also showed a significant independent association with high RNA expression of other immune modulator proteins, namely, PD-L1 immunohistochemistry (IHC) ≥1 (odds ratio (OR) 2.15, P=0.008), CTLA4 (OR=2.17, P=0.05) and OX40 high RNA expression (OR=2.64, P=0.001). Overall, these results suggest that breast and lung cancer have a high proportion of patients with a GITR and GITR-L RNA expression profile that merits further investigation in GITR agonism studies. The association of high GITR expression with high CTLA4 and OX40 RNA expression, as well as positive PD-L1 IHC, provides a rationale for a combination approach targeting these specific immune modulator proteins in patients whose tumors show such co-expression.

Reverse repurposing: Potential utility of cancer drugs in nonmalignant illnesses.

Growth and immune process dysregulation can result in both cancer and nonmalignant disease (hereditary or acquired, with and without predisposition to malignancy). Moreover, perhaps unexpectedly, many nonmalignant illnesses harbor genomic alterations indistinguishable from druggable oncogenic drivers. Therefore, targeted compounds used successfully to treat cancer may have therapeutic potential for nonmalignant conditions harboring the same target. MEK, PI3K/AKT/mTOR, fibroblast growth factor receptor (FGFR), and NRG1/ERBB pathway genes have all been implicated in both cancer and noncancerous conditions, and several cognate antagonists, as well as Bruton's tyrosine kinase inhibitors, JAK inhibitors, and CD20-directed antibodies, have established or theoretical therapeutic potential to bridge cancer and benign diseases. Intriguingly, pharmacologically tractable cancer drivers characterize a wide spectrum of disorders without malignant potential, including but not limited to Alzheimer's disease and a variety of other neurodegenerative conditions, rheumatoid arthritis, achondroplastic dwarfism, and endometriosis. Expanded repositioning of oncology agents in order to benefit benign but serious medical illnesses is warranted.

Brief Report: Dolutegravir Plasma Protein Binding and Unbound Concentrations During Pregnancy and Postpartum.

BACKGROUND: Clinical interpretation of the reduced dolutegravir (DTG) plasma concentrations reported during pregnancy is complicated by its high plasma protein binding. Plasma proteins significantly decrease during pregnancy, and understanding changes in DTG protein binding and its therapeutically active unbound concentrations are necessary to evaluate the impact of pregnancy changes on DTG pharmacokinetics. METHODS: Retrospective assessment of plasma samples from pregnant women living with HIV enrolled in the International Maternal Pediatric Adolescent AIDS Clinical Trials Network P1026s study receiving 50 mg DTG film-coated tablets once daily as part of clinical care. Unbound and total DTG concentrations were determined predose (C0) and at maximum (Cmax) concentrations during the second trimester (2T), third trimester (3T), and postpartum (PP). Percentage unbound was calculated as the ratio of ultrafiltrate unbound DTG concentration to total DTG concentration. RESULTS: Twenty-nine mothers were included for protein binding evaluations; 15, 27, and 23 from the 2T, 3T, and PP, respectively. DTG % unbound for C0 and Cmax were significantly different by stage of pregnancy, with 3T significantly higher compared with PP; 1.02% vs. 0.69% (P = 0.0067) for C0 and 0.76% vs. 0.46% for Cmax (P = 0.0056). Median (IQR) unbound concentrations for C0 were 6.3 (4.7-18.4) for the 2T, 8.0 (5.6-16.9) for the 3T, and 13.3 (8.4-22.7) ng/mL PP, significantly different between 2T and PP (P = 0.0039), but not different between 3T and PP (P = 0.46). CONCLUSION: Lower total DTG plasma concentrations during pregnancy coincide with temporal decreases in DTG protein binding, resulting in comparable unbound DTG concentrations during the 3T and PP.

At the right dose: personalised (N-of-1) dosing for precision oncology.

The objective of oncology therapeutics, especially in the age of precision medicine, is to give the right drug(s) to the right patient at the right time. Yet, a major challenge is finding the right dose for each patient. Determining safe and efficacious doses of oncology treatments, especially for novel combination therapies, can be challenging. Moreover, traditionally, dosing cancer drugs is based on giving each patient the same dose (a flat dose) or a dose based on surface area/weight. But patients' ability to tolerate drugs is influenced by additional factors including, but not limited to age, gender, race, comorbidities, organ function, and metabolism. Herein, we present evidence that, in the era of targeted drugs, individualised drug dosing determined by starting at reduced doses and using intrapatient dose escalation can yield safe and effective personalised dosing of novel combinations of approved drugs that have not previously undergone formal phase I trials and can also optimise dosing of tested drug regimens.

Variable Delta-9-Tetrahydrocannabinol Pharmacokinetics and Pharmacodynamics After Cannabis Smoking in Regular Users.

BACKGROUND: Despite its federally restricted status, cannabis is widely used medicinally and recreationally. The pharmacokinetics (PK) and central nervous system (CNS) effects of tetrahydrocannabinol (THC), the major psychoactive cannabinoid, are not well understood. The objective of this study was to develop a population PK model of inhaled THC, including sources of variability, and to conduct an exploratory analysis of potential exposure-response relationships. METHODS: Regular adult cannabis users smoked a single cannabis cigarette containing 5.9% THC (Chemovar A) or 13.4% THC (Chemovar B) ad libitum. THC concentrations in whole blood were measured and used to develop a population PK model to identify potential factors contributing to interindividual variability in THC PK and to describe THC disposition. Relationships between model-predicted exposure and heart rate, change in composite driving score on a driving simulator, and perceived highness were evaluated. RESULTS: From the 102 participants, a total of 770 blood THC concentrations were obtained. A two-compartment structural model adequately fit the data. Chemovar and baseline THC (THC BL ) were found to be significant covariates for bioavailability, with Chemovar A having better THC absorption. The model predicted that heavy users-those with the highest THC BL -would have significantly higher absorption than those with lighter previous use. There was a statistically significant relationship between exposure and heart rate, and exposure and perceived highness. CONCLUSIONS: THC PK is highly variable and related to baseline THC concentrations and different chemovars. The developed population PK model showed that heavier users had higher THC bioavailability. To better understand the factors affecting THC PK and dose-response relationships, future studies should incorporate a wide range of doses, multiple routes of administration, and different formulations relevant to typical community use.

Dosing of 3 Targeted Agents in Novel Drug Combinations Used at the Precision Medicine Clinic of the University of California San Diego.

BACKGROUND: The diversity in the genomic landscape of advanced and metastatic tumors calls for combination therapies based on the genomic signature associated with each tumor. Determining safe and tolerable doses for novel combinations of oncology drugs is essential for a precision medicine approach, but can also require dose reductions. Trametinib, palbociclib, and everolimus are among the targeted therapies most often used in novel combinations at our precision medicine clinic. OBJECTIVE: To evaluate the safe, tolerable dosing of trametinib, palbociclib, and everolimus when used as part of novel combinations with other agents for the treatment of advanced or metastatic solid tumors. METHODS: This retrospective study included adult patients with advanced or metastatic solid tumors who received trametinib, everolimus, or palbociclib plus other therapies as a part of novel combinations between December 2011 and July 2018 at the University of California San Diego. Patients were excluded if they received trametinib, everolimus, or palbociclib in standard combinations, such as dabrafenib plus trametinib, everolimus plus fulvestrant, everolimus plus letrozole, and palbociclib plus letrozole. Dosing and adverse events were determined through a review of the electronic medical records. A safe, tolerable drug combination dose was defined as being tolerated for at least 1 month, with no clinically significant serious adverse events. RESULTS: A safe, tolerable dose was determined for 76% of the 71 patients who received trametinib, 88% of the 48 patients who received everolimus, and 73% of the 41 patients receiving palbociclib when used in combination with other therapies. For patients with clinically significant adverse events, dose reductions were attempted in 30% of the trametinib recipients, in 17% of everolimus recipients, and in 45% of palbociclib recipients. When used in combination with other therapies, the optimal dosing of trametinib, palbociclib, and everolimus was lower than the standard single-agent dosing: it was 1 mg daily for trametinib; 5 mg daily for everolimus; and 75 mg daily, for 3 weeks on and 1 week off for palbociclib. Of note, everolimus could not be given concomitantly with trametinib at these doses. CONCLUSION: Safe and tolerable dosing of novel combination therapies that includes trametinib, everolimus, or palbociclib is feasible for a precision medicine approach. However, neither results from this study nor results from previous studies could support the use of everolimus in combination with trametinib, even at reduced doses.

Fexofenadine Plasma Concentrations to Estimate Systemic Exposure in Healthy Adults Using a Limited Sampling Strategy with a Population Pharmacokinetic Approach.

BACKGROUND: Fexofenadine is a recommended in vivo probe drug for phenotyping P-glycoprotein (P-gp) and organic anion transporting polypeptide (OATP) 1B1/3 transporter activities. This study evaluated a limited sampling strategy using a population pharmacokinetic approach to estimate plasma fexofenadine exposure as an index of P-gp and OATP activities. METHODS: In a previous study, a single oral dose of fexofenadine (120 mg) was administered alone or in combination with grapefruit juice, Panax ginseng , or Echinacea purpurea to healthy adult participants. Serial plasma samples were collected up to 72 hours after administration and fexofenadine concentrations were measured. A population pharmacokinetic model was developed using nonlinear mixed-effects modeling. Limited sampling models (LSMs) using single and 2-timepoint fexofenadine concentrations were compared with full profiles from intense sampling using empirical Bayesian post hoc estimations of systemic exposure derived from the population pharmacokinetic model. Predefined criteria for LSM selection and validation included a coefficient of determination (R 2 ) ≥ 0.90, relative percent mean prediction error ≥ -5 to ≤5%, relative percent mean absolute error ≤ 10%, and relative percent root mean square error ≤ 15%. RESULTS: Fexofenadine concentrations (n = 1520) were well described using a 2-compartment model. Grapefruit juice decreased the relative oral bioavailability of fexofenadine by 25%, whereas P. ginseng and E. purpurea had no effect. All the evaluated single timepoint fexofenadine LSMs showed unacceptable percent mean prediction error, percent mean absolute error, and/or percent root mean square error. Although adding a second time point improved precision, the predefined criteria were not met. CONCLUSIONS: Identifying novel fexofenadine LSMs to estimate P-gp and OATP1B1/3 activities in healthy adults for future transporter-mediated drug-drug interaction studies remains elusive.

Liquid biopsy: current technology and clinical applications.

Liquid biopsies are increasingly used for cancer molecular profiling that enables a precision oncology approach. Circulating extracellular nucleic acids (cell-free DNA; cfDNA), circulating tumor DNA (ctDNA), and circulating tumor cells (CTCs) can be isolated from the blood and other body fluids. This review will focus on current technologies and clinical applications for liquid biopsies. ctDNA/cfDNA has been isolated and analyzed using many techniques, e.g., droplet digital polymerase chain reaction, beads, emulsion, amplification, and magnetics (BEAMing), tagged-amplicon deep sequencing (TAm-Seq), cancer personalized profiling by deep sequencing (CAPP-Seq), whole genome bisulfite sequencing (WGBS-Seq), whole exome sequencing (WES), and whole genome sequencing (WGS). CTCs have been isolated using biomarker-based cell capture, and positive or negative enrichment based on biophysical and other properties. ctDNA/cfDNA and CTCs are being exploited in a variety of clinical applications: differentiating unique immune checkpoint blockade response patterns using serial samples; predicting immune checkpoint blockade response based on baseline liquid biopsy characteristics; predicting response and resistance to targeted therapy and chemotherapy as well as immunotherapy, including CAR-T cells, based on serial sampling; assessing shed DNA from multiple metastatic sites; assessing potentially actionable alterations; analyzing prognosis and tumor burden, including after surgery; interrogating difficult-to biopsy tumors; and detecting cancer at early stages. The latter can be limited by the small amounts of tumor-derived components shed into the circulation; furthermore, cfDNA assessment in all cancers can be confounded by clonal hematopoeisis of indeterminate potential, especially in the elderly. CTCs can be technically more difficult to isolate that cfDNA, but permit functional assays, as well as evaluation of CTC-derived DNA, RNA and proteins, including single-cell analysis. Blood biopsies are less invasive than tissue biopsies and hence amenable to serial collection, which can provide critical molecular information in real time. In conclusion, liquid biopsy is a powerful tool, and remarkable advances in this technology have impacted multiple aspects of precision oncology, from early diagnosis to management of refractory metastatic disease. Future research may focus on fluids beyond blood, such as ascites, effusions, urine, and cerebrospinal fluid, as well as methylation patterns and elements such as exosomes.

Maraviroc Population Pharmacokinetics Within the First 6 Weeks of Life.

BACKGROUND: Treatment and prophylaxis options for neonatal HIV are limited. This study aimed to develop a population pharmacokinetic model to characterize the disposition of maraviroc in neonates to inform dosing regimens and expand available options. METHODS: Using maraviroc concentrations from neonates who received either a single dose or multiple doses of 8 mg/kg of maraviroc in the first 6 weeks of life, a population pharmacokinetic model was developed to determine the effects of age, sex, maternal efavirenz exposure and concomitant ARV therapy on maraviroc disposition. The final model was used in Monte Carlo simulations to generate expected exposures with recommended dosing regimens. RESULTS: A total of 396 maraviroc concentrations, collected in the first 4 days of life, at 1 week, at 4 weeks and at 6 weeks, from 44 neonates were included in the analysis. After allometrically scaling for weight, age less than 4 days was associated with a 44% decreased apparent clearance compared with participants 7 days to 6 weeks of life. There were no differences identified in apparent clearance or volume of distribution from ages 7 days to 6 weeks, sex, maternal efavirenz exposure or concomitant nevirapine therapy. Monte Carlo simulations with FDA-approved weight band dosing resulted in the majority of simulated patients (84.3%) achieving an average concentration of ≥75 ng/mL. CONCLUSIONS: While maraviroc apparent clearance is decreased in the first few days of life, the current FDA-approved maraviroc weight band dosing provides maraviroc exposures for neonates in the first 6 weeks of life, which were consistent with adult maraviroc exposure range. Maraviroc provides another antiretroviral treatment option for very young infants.

Combination high-dose interleukin-2 and nivolumab for programmed cell death-1 refractory metastatic melanoma: a case series.

BACKGROUND: Therapeutic options are needed for metastatic melanoma refractory to therapies directed against programmed cell death-1. High-dose interleukin-2 has the potential to overcome programmed cell death-1 resistance. CASE PRESENTATION: We report three consecutive Caucasian patients, two female (60 and 55 years old) and one male (56 years old), refractory to anti-programmed cell death-1 therapy who were treated with concurrent nivolumab and standard-dosing bolus high-dose interleukin-2. We did not see any unexpected toxicities with overlapping treatments as compared with either high-dose interleukin-2 or nivolumab alone. CONCLUSIONS: The tolerance and disease control observed among the three patients in this limited series support formal exploration of this combination.

Cetuximab in Patients with Non-Small Cell Lung Cancer and EGFR Exon 20 Insertion Alterations.

Epidermal Growth Factor Receptor (EGFR) exon 20 insertion alterations represent 4%-10% of all EGFR mutations in Non-Small Cell Lung Cancer (NSCLC) and result in resistance to standard EGFR-directed therapies. EGFR exon 20 insertions restrict the size of the kinase pocket, prohibiting the entry of approved EGFR kinase inhibitor drugs. Structural In Silico modeling also predicts that EGFR exon 20 insertion anomalies increase attractive electrostatic dimerization, hence stabilizing the activating dimer configuration. EGFR antibodies such as cetuximab that interfere with dimerization may lead to responses. We identified three non-smoking patients with NSCLC and EGFR exon 20 insertions treated with cetuximab-based therapy. All three patients demonstrated clinical benefit. A 58-year-old woman achieved prolonged stable disease lasting 9 months, while a 76-year-old woman and 38-year-old man maintained a partial response with progression-free survivals of 13 months and 32 months, respectively. In conclusion, cetuximab merits further investigation as it appears to be an additional promising therapy for overcoming EGFR exon 20 insertion-related resistance.

Optimizing Dolutegravir Initiation in Neonates Using Population Pharmacokinetic Modeling and Simulation.

BACKGROUND: A knowledge gap exists for dolutegravir (DTG) pharmacokinetics and safety during the first 4 weeks of life, preventing safe and effective DTG use in neonates. SETTING: Population pharmacokinetic modeling and simulation were used to assess newborn DTG dosing requirements during the first few days of life as a function of maternal DTG dosing history before delivery. METHODS: DTG PK data were obtained from pregnant women and infants enrolled in the International Maternal Pediatric Adolescent AIDS Clinical Trials Network P1026S study. Maternal and neonate population pharmacokinetic models were separately developed. Monte Carlo simulations were performed to simulate neonatal concentrations after 2 doses of DTG after birth for infants born to mothers either receiving or not receiving DTG before delivery. RESULTS: In DTG-naïve infants, a 5-mg DTG dose at birth with a second dose after 48 hours maintained median concentrations above the lower bound of the target range (0.77 µg/mL) and below the upper bound of the target range (7.34 µg/mL representing 2-fold above the adult Cmax value). In DTG-exposed infants, a 5-mg DTG dose at 24 hours after birth with a second dose after 48 hours maintained median concentrations within or nearly within the target range, even if the last maternal DTG dose was taken as soon as 6 hours or as long as 24 hours before delivery. CONCLUSIONS: Newborn DTG dosing requirements during the first few days of life depend on maternal DTG dosing history before delivery. These results may help the design of future clinical studies of DTG in the neonatal population.

Impact of CYP2B6 genotype, tuberculosis therapy, and formulation on efavirenz pharmacokinetics in infants and children under 40 months of age.

OBJECTIVE: Dosing efavirenz (EFV) in children less than 3 years of age is challenging due to large variability in drug levels. This study evaluated differences in pharmacokinetics with tuberculosis (TB) therapy, formulation, age, and CYP2B6 genotype. DESIGN: Pharmacokinetic data from three IMPAACT/PACTG studies (P382, P1021, and P1070) for children initiating therapy less than 40 months of age were evaluated. METHODS: Pharmacokinetic data were combined in a population pharmacokinetic model. Exposure from the 2-week pharmacokinetic visit was compared with changes in viral RNA between the Week 0 and Week 4 visits. RESULTS: The model included 103 participants (19 on TB therapy). CYP2B6 516 genotype information was available for 82 participants (TT: 15, GT: 28, GG: 39). Median age at the first pharmacokinetic visit was 17.0 months (range: 2.0-39.0 months). Liquid formulation led to a 42% decrease in bioavailability compared with opened capsules. TB therapy (isoniazid and rifampin) led to a 29% decreased clearance, however Monte Carlo simulations demonstrated the majority of participants on TB therapy receiving standard EFV dosing to be in the target area under the curve range. Clearance was 5.3-fold higher for GG than TT genotype and 3.3-fold higher for GT than TT genotype. Age did not have a significant effect on clearance in the final model. Initial viral RNA decay was lower for patients in the lowest quartile of exposures (area under the curves) than for higher quartiles (P = 0.013). CONCLUSION: EFV dosing should account for CYP2B6 516 genotype and formulation, but does not require adjustment for concurrent TB therapy.

Molecular profiling of advanced malignancies guides first-line N-of-1 treatments in the I-PREDICT treatment-naïve study.

BACKGROUND: Malignancies are molecularly complex and become more resistant with each line of therapy. We hypothesized that offering matched, individualized combination therapies to patients with treatment-naïve, advanced cancers would be feasible and efficacious. Patients with newly diagnosed unresectable/metastatic, poor-prognosis cancers were enrolled in a cross-institutional prospective study. METHODS: A total of 145 patients were included in the study. Genomic profiling (tissue and/or circulating tumor DNA) was performed in all patients, and PD-L1 immunohistochemistry, tumor mutational burden, and microsatellite status assessment were performed in a subset of patients. We evaluated safety and outcomes: disease-control rate (stable disease for ≥ 6 months or partial or complete response), progression-free survival (PFS), and overall survival (OS). RESULTS: Seventy-six of 145 patients (52%) were treated, most commonly for non-colorectal gastrointestinal cancers, carcinomas of unknown primary, and hepatobiliary malignancies (53% women; median age, 63 years). The median number of deleterious genomic alterations per patient was 5 (range, 0-15). Fifty-four treated patients (71%) received ≥ 1 molecularly matched therapy, demonstrating the feasibility of administering molecularly matched therapy. The Matching Score, which reflects the percentage of targeted alterations, correlated linearly with progression-free survival (R2 = 0.92; P = 0.01), and high (≥ 60%) Matching Score was an independent predictor of improved disease control rate [OR 3.31 (95% CI 1.01-10.83), P = 0.048], PFS [HR 0.55 (0.28-1.07), P = 0.08], and OS [HR 0.42 (0.21-0.85), P = 0.02]. Serious adverse event rates were similar in the unmatched and matched groups. CONCLUSIONS: Personalized combination therapies targeting a majority of a patient's molecular alterations have antitumor activity as first-line treatment. These findings underscore the feasibility and importance of using tailored N-of-1 combination therapies early in the course of lethal malignancies. TRIAL REGISTRATION: I-PREDICT ( NCT02534675 ) was registered on August 25, 2015.

BRAF V600E/V600K Mutations versus Nonstandard Alterations: Prognostic Implications and Therapeutic Outcomes.

BRAF and MEK inhibitors are standard of care for BRAF V600E/K-mutated melanoma, but the benefit of BRAF and/or MEK inhibitors for nonstandard BRAF alterations for melanoma and other cancers is unclear. Patients with diverse malignancies whose cancers had undergone next-generation sequencing were screened for BRAF alterations. Demographics, treatment with BRAF and/or MEK inhibitors, clinical response, progression-free survival (PFS), and overall survival (OS) were determined from review of the electronic medical records for patients with standard BRAF V600E/K versus nonstandard BRAF alterations. A total of 213 patients with BRAF alterations (87 with nonstandard alterations) were identified; OS from diagnosis was significantly worse with nonstandard BRAF versus standard alterations, regardless of therapy [HR (95% confidence interval), 0.58 (0.38-0.88); P = 0.01]. Overall, 45 patients received BRAF/MEK-directed therapy (eight with nonstandard alterations); there were no significant differences in clinical benefit rate [stable disease ≥6 months/partial/complete response (74% vs. 63%; P = 0.39) or PFS (P = 0.24; BRAF V600E/K vs. others)]. In conclusion, patients with nonstandard versus standard BRAF alterations (BRAF V600E/K) have a worse prognosis with shorter survival from diagnosis. Even so, 63% of patients with nonstandard BRAF alterations achieved clinical benefit with BRAF/MEK inhibitors. Larger prospective studies are warranted to better understand the prognostic versus predictive implication of standard versus nonstandard BRAF alterations.

S-warfarin limited sampling strategy with a population pharmacokinetic approach to estimate exposure and cytochrome P450 (CYP) 2C9 activity in healthy adults.

PURPOSE: S-warfarin is used to phenotype cytochrome P450 (CYP) 2C9 activity. This study evaluated S-warfarin limited sampling strategy with a population pharmacokinetic (PK) approach to estimate CYP2C9 activity in healthy adults. METHODS: In 6 previously published studies, a single oral dose of warfarin 10 mg was administered alone or with a CYP2C9 inducer to 100 healthy adults. S-warfarin concentrations were obtained from adults during conditions when subjects were not on any prescribed medications. A population PK model was developed using non-linear mixed effects modeling. Limited sampling models (LSMs) using single- or 2-timepoint concentrations were compared with full PK profiles from intense sampling using empiric Bayesian post hoc estimations of S-warfarin AUC derived from the population PK model. Preset criterion for LSM selection and validation were a correlation coefficient (R2) >0.9, relative percent mean prediction error (%MPE) >-5 to <5%, relative percent mean absolute error (%MAE) ≤ 10%, and relative percent root mean squared error (%RMSE) ≤ 15%. RESULTS: S-warfarin concentrations (n=2540) were well described with a two-compartment model. Mean apparent oral clearance was 0.56 L/hr and volume of distribution was 35.5 L. Clearance decreased 33% with the CYP2C9 *3 allele and increased 42% with lopinavir/ritonavir co-administration. During CYP2C9 constitutive conditions, LSMs at 48 hr and at 72 hr as well as 2-timepoint LSMs were within acceptable limits for R2, %MPE, %MAE, and %RMSE. During CYP2C9 induction, S-warfarin LSMs had unacceptable %MPE, %MAE, and %RMSE. CONCLUSIONS: Phenotyping studies with S-warfarin in healthy subjects can utilize a single- and/or a 2-timepoint LSM with a population PK approach to estimate constitutive CYP2C9 activity.

Clinical implications of plasma circulating tumor DNA in gynecologic cancer patients.

Molecular characterization of cancers is important in dictating prognostic factors and directing therapy. Next-generation sequencing of plasma circulating tumor DNA (ctDNA) offers less invasive, more convenient collection, and a more real-time representation of a tumor and its molecular heterogeneity than tissue. However, little is known about the clinical implications of ctDNA assessment in gynecologic cancer. We describe the molecular landscape identified on ctDNA, ctDNA concordance with tissue-based analysis, and factors associated with overall survival (OS) in gynecologic cancer patients with ctDNA analysis. We reviewed clinicopathologic and genomic information for 105 consecutive gynecologic cancer patients with ctDNA analysis, including 78 with tissue-based sequencing, enrolled in the Profile-Related Evidence Determining Individualized Cancer Therapy (NCT02478931) trial at the University of California San Diego Moores Cancer Center starting July 2014. Tumors included ovarian (47.6%), uterine (35.2%), cervical (12.4%), vulvovaginal (2.9%), and unknown gynecologic primary (1.9%). Most ovarian and uterine cancers (86%) were high grade. 34% (N = 17) of ovarian cancers had BRCA alterations, and 22% (N = 11) were platinum sensitive. Patients received median 2 (range 0-13) lines of therapy prior to ctDNA collection. Most (75.2%) had at least one characterized alteration on ctDNA analysis, and the majority had unique genomic profiles on ctDNA. Most common alterations were TP53 (N = 59, 56.2% of patients), PIK3CA (N = 26, 24.8%), KRAS (N = 14, 13.3%), BRAF (N = 10, 9.5%), ERBB2 (N = 8, 7.6%), and MYC (N = 8, 7.6%). Higher ctDNA maximum mutation allele frequency was associated with worse OS [hazard ratio (HR): 1.91, P = 0.03], while therapy matched to ctDNA alterations (N = 33 patients) was independently associated with improved OS (HR: 0.34, P = 0.007) compared to unmatched therapy (N = 28 patients) in multivariate analysis. Tissue and ctDNA genomic results showed high concordance unaffected by temporal or spatial factors. This study provides evidence for the utility of ctDNA in determining outcome and individualizing cancer therapy in patients with gynecologic cancer.

Model Informed Development of VRC01 in Newborn Infants Using a Population Pharmacokinetics Approach.

VRC01 is a first-in-class, potent, broadly neutralizing antibody that targets the CD4 binding site of gp120 on HIV-1 viruses, and is under development as a novel HIV therapeutic. This study utilized population pharmacokinetic (PK) modeling to characterize VRC01 PK to guide dosing selection for ongoing phase II clinical trials in pediatric patients. Combining VRC01 PK data from 3 adult and 1 infant clinical trials, a total of 1,475 VRC01 serum concentrations from 100 participants were used in the analysis (40 infants and 60 adults). VRC01 was administered either i.v. or s.c. (1-40 mg/kg). All infants received s.c. doses as compared with 13% s.c. and 87% i.v. in adults. The data were well-described by a two-compartment model. Clearance was 37% higher in adults with HIV infection and 83% lower in infants than adults. Subcutaneous bioavailability was 55% in adults. Rapid absorption was seen in infants indicating therapeutic levels could be achieved quickly. Monte Carlo simulations were used to determine optimal dosing and demonstrated 40 mg/kg s.c. at weeks 0, 2, 6, and 10 would maintain VRC01 levels at the suppressive target concentration of 50 µg/mL for the first 14 weeks of life in infants. The current analysis provides new insight into differences in monoclonal antibody PK between infants and adults and demonstrates the utility of a population PK approach in informing drug development for infant populations.