Mass Balance, Metabolic Pathways, Absolute Bioavailability, and Pharmacokinetics of Giredestrant in Healthy Subjects.

Giredestrant is a potent and selective small-molecule estrogen receptor degrader. The objectives of this study were to assess the absolute bioavailability (aBA) of giredestrant and to determine the mass balance, routes of elimination, and metabolite profile of [14C]giredestrant. In part 1 (mass balance), a single 30.8-mg oral dose of [14C]giredestrant (105 µCi) was administered to women of nonchildbearing potential (WNCBP; n = 6). The mean recovery of total radioactivity in excreta was 77.0%, with 68.0% of the dose excreted in feces and 9.04% excreted in urine over a 42-day sample collection period. The majority of the circulating radioactivity (56.8%) in plasma was associated with giredestrant. Giredestrant was extensively metabolized, with giredestrant representing only 20.0% and 1.90% of the dose in feces and urine, respectively. All metabolites in feces resulted from oxidative metabolism and represented 44.7% of the dose. In part 2 (aBA), WNCBP (n = 10) received an oral (30-mg capsule) or intravenous (30-mg solution) dose of giredestrant. The aBA of giredestrant after oral administration was 58.7%. Following the intravenous dose, giredestrant had a plasma clearance and volume of distribution of 5.31 L/h and 266 L, respectively. In summary, giredestrant was well tolerated, rapidly absorbed, and showed moderate oral bioavailability with low recovery of the dose as parent drug in excreta. Oxidative metabolism followed by excretion in feces was identified as the major route of elimination of giredestrant. SIGNIFICANCE STATEMENT: This study provides definitive insight into the absorption, distribution, metabolism, and excretion of giredestrant in humans. The results show that giredestrant exhibits low clearance, a high volume of distribution, and moderate oral bioavailability in humans. In addition, the data show that oxidative metabolism followed by excretion in feces is the primary elimination route of giredestrant in humans. These results will be used to further inform the clinical development of giredestrant.

The Absolute Bioavailability and Absorption, Metabolism, and Excretion of Ipatasertib, a Potent and Highly Selective Protein Kinase B (Akt) Inhibitor.

Ipatasertib (GDC-0068) is a potent, highly selective, small-molecule inhibitor of protein kinase B (Akt) being developed by Genentech/Roche as a single agent and in combination with other therapies for the treatment of cancers. To fully understand the absorption, metabolism, and excretion of ipatasertib in humans, an open-label study using 14C-radiolabeled ipatasertib was completed to characterize the absolute bioavailability (period 1) and mass balance and metabolite profiling (period 2). In period 1, subjects were administered a 200 mg oral dose of ipatasertib followed by an 80 µg (800 nCi) intravenous dose of [14C]-ipatasertib. In period 2, subjects received a single oral dose containing approximately 200 mg (100 µCi) [14C]-ipatasertib. In an integrated analytical strategy, accelerator mass spectrometry was applied to measure the 14C microtracer intravenous pharmacokinetics in period 1 and fully profile plasma radioactivity in period 2. The systemic plasma clearance and steady-state volume of distribution were 98.8 L/h and 2530 L, respectively. The terminal half-lives after oral and intravenous administrations were similar (26.7 and 27.4 hours, respectively) and absolute bioavailability of ipatasertib was 34.0%. After a single oral dose of [14C]-ipatasertib, 88.3% of the administered radioactivity was recovered with approximately 69.0% and 19.3% in feces and urine, respectively. Radioactivity in feces and urine was predominantly metabolites with 24.4% and 8.26% of dose as unchanged parent, respectively; indicating that ipatasertib had been extensively absorbed and hepatic metabolism was the major route of clearance. The major metabolic pathway was N-dealkylation mediated by CYP3A, and minor pathways were oxidative by cytochromes P450 and aldehyde oxidase. SIGNIFICANCE STATEMENT: The study provided definitive information regarding the absolute bioavailability and the absorption, metabolism, and excretion pathways of ipatasertib, a potent, novel, and highly selective small-molecule inhibitor of protein kinase B (Akt). An ultrasensitive radioactive counting method, accelerator mass spectrometry was successfully applied for 14C-microtracer absolute bioavailability determination and plasma metabolite profiling.

Evaluation of Ipatasertib Interactions with Itraconazole and Coproporphyrin I and III in a Single Drug Interaction Study in Healthy Subjects.

Ipatasertib is a pan-AKT inhibitor in development for the treatment of cancer. Ipatasertib was metabolized by CYP3A4 to its major metabolite, M1 (G-037720), and was a P-gp substrate and OATP1B1/1B3 inhibitor in vitro. A phase I drug-drug interaction (DDI) study (n = 15) was conducted in healthy subjects to evaluate the effect of itraconazole (200-mg solution QD, 4 days), a strong CYP3A4 and P-gp inhibitor, on pharmacokinetics of ipatasertib (100-mg single dose). Itraconazole increased the Cmax and AUC0 -∞ of ipatasertib by 2.3- and 5.5-fold, respectively, increased the half-life by 53%, and delayed the tmax by 1 hour. The Cmax and AUC0-72h of its metabolite M1 (G-037720) reduced by 91% and 68%, respectively. This study confirmed that CYP3A4 plays a major role in ipatasertib clearance. Furthermore, the interaction of ipatasertib with coproporphyrin (CP) I and CPIII, the two endogenous substrates of OATP1B1/1B3, was evaluated in this study. CPI and CPIII plasma levels were unchanged in the presence of ipatasertib, both at exposures of 100 mg and at higher exposures in combination with itraconazole. This indicated no in vivo inhibition of OATP1B1/1B3 by ipatasertib. Additionally, it was shown that CPI and CPIII were not P-gp substrates in vitro, and itraconazole had no effect on CPI and CPIII concentrations in vivo. The latter is an important finding because it will simplify interpretation of future DDI studies using CPI/CPIII as OATP1B1/1B3 biomarkers. SIGNIFICANCE STATEMENT: This drug-drug interaction study in healthy volunteers demonstrated that CYP3A4 plays a major role in ipatasertib clearance, and that ipatasertib is not an organic anion transporting polypeptide 1B1/1B3 inhibitor. Furthermore, it was demonstrated that itraconazole, an inhibitor of CYP3A4 and several transporters, did not affect CPI/CPIII levels in vivo. This increases the understanding and application of these endogenous substrates as well as itraconazole in complex drug interaction studies.

A phase Ib open-label dose escalation study of the safety, pharmacokinetics, and pharmacodynamics of cobimetinib (GDC-0973) and ipatasertib (GDC-0068) in patients with locally advanced or metastatic solid tumors.

BACKGROUND: This Phase Ib study explored combination dosing of the allosteric MEK1/2 inhibitor cobimetinib and the ATP-competitive pan-AKT inhibitor ipatasertib. METHODS: Patients with advanced solid tumors were enrolled to two dose escalation arms, each using a 3 + 3 design in 28-day cycles. In Arm A, patients received concurrent cobimetinib and ipatasertib on days 1-21. In Arm B, cobimetinib was administered intermittently with ipatasertib for 21 days. Primary objectives evaluated dose-limiting toxicities (DLTs), maximum tolerated doses (MTD), and the recommended Phase II dose (RP2D). Secondary objectives included analysis of pharmacokinetic parameters, MAPK and PI3K pathway alterations, changes in tissue biomarkers, and preliminary anti-tumor efficacy. Expansion cohorts included patients with PTEN-deficient triple-negative breast cancer and endometrial cancer. RESULTS: Among 66 patients who received ≥1 dose of study drug, all experienced an adverse event (AE). Although no DLTs were reported, 6 patients experienced Cycle 1 DLT-equivalent AEs. The most common treatment-related AEs were diarrhea, nausea, vomiting, dermatitis acneiform, and fatigue. Thirty-five (53%) patients experienced drug-related AEs of ≥ grade 3 severity. Cobimetinb/ipatasertib MTDs were 60/200 mg on Arm A and 150/300 mg on Arm B; the latter was chosen as the RP2D. No pharmacokinetic interactions were identified. Biomarker analyses indicated pathway blockade and increases in IFNγ and PD-L1 gene expression following the combination. Three patients with endometrial or ovarian cancer achieved partial response, all with PTEN-low disease and two with tumor also harboring KRAS mutation. CONCLUSION: There was limited tolerability and efficacy for this MEK and AKT inhibitor combination. Nonetheless, pharmacodynamic analyses indicated target engagement and suggest rationale for further exploration of cobimetinib or ipatasertib in combination with other anticancer agents. ClinicalTrials.gov identifier: NCT01562275.

Calibrating the In Vitro-In Vivo Correlation for OATP-Mediated Drug-Drug Interactions with Rosuvastatin Using Static and PBPK Models.

Organic anion-transporting polypeptide (OATP) 1B1/3-mediated drug-drug interaction (DDI) potential is evaluated in vivo with rosuvastatin (RST) as a probe substrate in clinical studies. We calibrated our assay with RST and estradiol 17-ß-D-glucuronide (E217ßG)/cholecystokinin-8 (CCK8) as in vitro probes for qualitative and quantitative prediction of OATP1B-mediated DDI potential for RST. In vitro OATP1B1/1B3 inhibition using E217ßG and CCK8 yielded higher area under the curve (AUC) ratio (AUCR) values numerically with the static model, but all probes performed similarly from a qualitative cutoff-based prediction, as described in regulatory guidances. However, the magnitudes of DDI were not captured satisfactorily. Considering that clearance of RST is also mediated by gut breast cancer resistance protein (BCRP), inhibition of BCRP was also incorporated in the DDI prediction if the gut inhibitor concentrations were 10 × IC50 for BCRP inhibition. This combined static model closely predicted the magnitude of RST DDI with root-mean-square error values of 0.767-0.812 and 1.24-1.31 with and without BCRP inhibition, respectively, for in vitro-in vivo correlation of DDI. Physiologically based pharmacokinetic (PBPK) modeling was also used to simulate DDI between RST and rifampicin, asunaprevir, and velpatasvir. Predicted AUCR for rifampicin and asunaprevir was within 1.5-fold of that observed, whereas that for velpatasvir showed a 2-fold underprediction. Overall, the combined static model incorporating both OATP1B and BCRP inhibition provides a quick and simple mathematical approach to quantitatively predict the magnitude of transporter-mediated DDI for RST for routine application. PBPK complements the static model and provides a framework for studying molecules when a dynamic model is needed. SIGNIFICANCE STATEMENT: Using 22 drugs, we show that a static model for organic anion-transporting polypeptide (OATP) 1B1/1B3 inhibition can qualitatively predict potential for drug-drug interaction (DDI) using a cutoff-based approach, as in regulatory guidances. However, consideration of both OATP1B1/3 and gut breast cancer resistance protein inhibition provided a better prediction of the magnitude of the transporter-mediated DDI of these inhibitors with rosuvastatin. Based on these results, we have proposed an empirical mechanistic-static approach for a more reliable prediction of transporter-mediated DDI liability with rosuvastatin that drug development teams can leverage.

Phase Ib study of the MEK inhibitor cobimetinib (GDC-0973) in combination with the PI3K inhibitor pictilisib (GDC-0941) in patients with advanced solid tumors.

Purpose We investigated the combination of the MEK inhibitor, cobimetinib, and the pan-PI3K inhibitor, pictilisib, in an open-label, phase Ib study. Experimental Design Patients with advanced solid tumors were enrolled in 3 dose escalation schedules: (1) both agents once-daily for 21-days-on 7-days-off ("21/7"); (2) intermittent cobimetinib and 21/7 pictilisib ("intermittent"); or (3) both agents once-daily for 7-days-on 7-days-off ("7/7"). Starting doses for the 21/7, intermittent, and 7/7 schedules were 20/80, 100/130, and 40/130 mg of cobimetinib/pictilisib, respectively. Nine indication-specific expansion cohorts interrogated the recommended phase II dose and schedule. Results Of 178 enrollees (dose escalation: n = 98), 177 patients were dosed. The maximum tolerated doses for cobimetinib/pictilisib (mg) were 40/100, 125/180, and not reached, for the 21/7, intermittent, and 7/7 schedules, respectively. Six dose-limiting toxicities included grade 3 (G3) elevated lipase, G4 elevated creatine phosphokinase, and G3 events including fatigue concurrent with a serious adverse event (SAE) of diarrhea, decreased appetite, and SAEs of hypersensitivity and dehydration. Common drug-related adverse events included nausea, fatigue, vomiting, decreased appetite, dysgeusia, rash, and stomatitis. Pharmacokinetic parameters of the drugs used in combination were unaltered compared to monotherapy exposures. Confirmed partial responses were observed in patients with BRAF-mutant melanoma (n = 1) and KRAS-mutant endometrioid adenocarcinoma (n = 1). Eighteen patients remained on study ≥6 months. Biomarker data established successful blockade of MAP kinase (MAPK) and PI3K pathways. The metabolic response rate documented by FDG-PET was similar to that observed with cobimetinib monotherapy. Conclusions Cobimetinib and pictilisib combination therapy in patients with solid tumors had limited tolerability and efficacy.

Association of body-mass index and outcomes in patients with metastatic melanoma treated with targeted therapy, immunotherapy, or chemotherapy: a retrospective, multicohort analysis.

BACKGROUND: Obesity has been linked to increased mortality in several cancer types; however, the relation between obesity and survival outcomes in metastatic melanoma is unknown. The aim of this study was to examine the association between body-mass index (BMI) and progression-free survival or overall survival in patients with metastatic melanoma who received targeted therapy, immunotherapy, or chemotherapy. METHODS: This retrospective study analysed independent cohorts of patients with metastatic melanoma assigned to treatment with targeted therapy, immunotherapy, or chemotherapy in randomised clinical trials and one retrospective study of patients treated with immunotherapy. Patients were classified according to BMI, following the WHO definitions, as underweight, normal, overweight, or obese. Patients without BMI and underweight patients were excluded. The primary outcomes were the associations between BMI and progression-free survival or overall survival, stratified by treatment type and sex. We did multivariable analyses in the independent cohorts, and combined adjusted hazard ratios in a mixed-effects meta-analysis to provide a precise estimate of the association between BMI and survival outcomes; heterogeneity was assessed with meta-regression analyses. Analyses were done on the predefined intention-to-treat population in the randomised controlled trials and on all patients included in the retrospective study. FINDINGS: The six cohorts consisted of a total of 2046 patients with metastatic melanoma treated with targeted therapy, immunotherapy, or chemotherapy between Aug 8, 2006, and Jan 15, 2016. 1918 patients were included in the analysis. Two cohorts containing patients from randomised controlled trials treated with targeted therapy (dabrafenib plus trametinib [n=599] and vemurafenib plus cobimetinib [n=240]), two cohorts containing patients treated with immunotherapy (one randomised controlled trial of ipilimumab plus dacarbazine [n=207] and a retrospective cohort treated with pembrolizumab, nivolumab, or atezolizumab [n=331]), and two cohorts containing patients treated with chemotherapy (two randomised controlled trials of dacarbazine [n=320 and n=221]) were classified according to BMI as normal (694 [36%] patients), overweight (711 [37%]), or obese (513 [27%]). In the pooled analysis, obesity, compared with normal BMI, was associated with improved survival in patients with metastatic melanoma (average adjusted hazard ratio [HR] 0·77 [95% CI 0·66-0·90] for progression-free survival and 0·74 [0·58-0·95] for overall survival). The survival benefit associated with obesity was restricted to patients treated with targeted therapy (HR 0·72 [0·57-0·91] for progression-free survival and 0·60 [0·45-0·79] for overall survival) and immunotherapy (HR 0·75 [0·56-1·00] and 0·64 [0·47-0·86]). No associations were observed with chemotherapy (HR 0·87 [0·65-1·17, pinteraction=0·61] for progression-free survival and 1·03 [0·80-1·34, pinteraction=0·01] for overall survival). The association of BMI with overall survival for patients treated with targeted and immune therapies differed by sex, with inverse associations in men (HR 0·53 [0·40-0·70]), but no associations observed in women (HR 0·85 [0·61-1·18, pinteraction=0·03]). INTERPRETATION: Our results suggest that in patients with metastatic melanoma, obesity is associated with improved progression-free survival and overall survival compared with those outcomes in patients with normal BMI, and that this association is mainly seen in male patients treated with targeted or immune therapy. These results have implications for the design of future clinical trials for patients with metastatic melanoma and the magnitude of the benefit found supports further investigation of the underlying mechanism of these associations. FUNDING: ASCO/CCF Young Investigator Award, ASCO/CCF Career Development Award, MD Anderson Cancer Center (MDACC) Melanoma Moonshot Program, MDACC Melanoma SPORE, and the Dr Miriam and Sheldon G Adelson Medical Research Foundation.

Correction to: Application of a Novel 'Make and Test in Parallel' Strategy to Investigate the Effect of Formulation on the Pharmacokinetics of GDC-0810 in Healthy Subjects.

The Publisher regrets the typesetting mistake of retaining incorrect text in the Figure 1 caption. The correct text for the caption is "Molecular Structure of GDC-0810 NMG Salt". The original article has been corrected.

Application of a Novel 'Make and Test in Parallel' Strategy to Investigate the Effect of Formulation on the Pharmacokinetics of GDC-0810 in Healthy Subjects.

PURPOSE: GDC-0810, administered orally, was used in Phase I and II clinical studies to treat estrogen receptor positive breast cancers. It contains N-methyl-D-glucamine (NMG) salt of GDC-0810 with 10% sodium lauryl sulfate (SLS) as a surfactant and 15% sodium bicarbonate (NaHCO3) as an alkalizing agent to aid dissolution. To improve the processability of the formulation and reduce potential mucosal irritation in future Phase III clinical studies, the salt form and the amount of excipient required further optimization. To achieve this, we employed a novel "Make and Test in Parallel" strategy that facilitated selecting formulation in a rapid timeframe. METHODS: RapidFACT®, a streamlined, data-driven drug product optimization platform was used to bridge Phase I/II and Phase III formulations of GDC-0810. Five prototype formulations, varying in either the form of active pharmaceutical ingredient and/or the levels of the excipients SLS and NaHCO3 were assessed. Uniquely, the specific compositions of formulations manufactured and dosed were selected in real-time from emerging clinical data. RESULTS: The study successfully identified a Phase III formulation with a reduced SLS content, which when administered following a low-fat meal, gave comparable pharmacokinetic exposure to the Phase I/II formulation administered under the same conditions. CONCLUSIONS: Our novel 'Make and Test in Parallel' approach enabled optimization of GDC-0810 formulation in a time- and cost-efficient fashion.

Absorption, Metabolism, Excretion, and the Contribution of Intestinal Metabolism to the Oral Disposition of [14C]Cobimetinib, a MEK Inhibitor, in Humans.

The pharmacokinetics, metabolism, and excretion of cobimetinib, a MEK inhibitor, were characterized in healthy male subjects (n = 6) following a single 20 mg (200 µCi) oral dose. Unchanged cobimetinib and M16 (glycine conjugate of hydrolyzed cobimetinib) were the major circulating species, accounting for 20.5% and 18.3% of the drug-related material in plasma up to 48 hours postdose, respectively. Other circulating metabolites were minor, accounting for less than 10% of drug-related material in plasma. The total recovery of the administered radioactivity was 94.3% (±1.6%, S.D.) with 76.5% (±2.3%) in feces and 17.8% (±2.5%) in urine. Metabolite profiling indicated that cobimetinib had been extensively metabolized with only 1.6% and 6.6% of the dose remaining as unchanged drug in urine and feces, respectively. In vitro phenotyping experiments indicated that CYP3A4 was predominantly responsible for metabolizing cobimetinib. From this study, we concluded that cobimetinib had been well absorbed (fraction absorbed, Fa = 0.88). Given this good absorption and the previously determined low hepatic clearance, the systemic exposures were lower than expected (bioavailability, F = 0.28). We hypothesized that intestinal metabolism had strongly attenuated the oral bioavailability of cobimetinib. Supporting this hypothesis, the fraction escaping gut wall elimination (Fg) was estimated to be 0.37 based on F and Fa from this study and the fraction escaping hepatic elimination (Fh) from the absolute bioavailability study (F = Fa × Fh × Fg). Physiologically based pharmacokinetics modeling also showed that intestinal clearance had to be included to adequately describe the oral profile. These collective data suggested that cobimetinib was well absorbed following oral administration and extensively metabolized with intestinal first-pass metabolism contributing to its disposition.

Combination of vemurafenib and cobimetinib in patients with advanced BRAF(V600)-mutated melanoma: a phase 1b study.

BACKGROUND: Addition of a MEK inhibitor to a BRAF inhibitor enhances tumour growth inhibition, delays acquired resistance, and abrogates paradoxical activation of the MAPK pathway in preclinical models of BRAF-mutated melanoma. We assessed the safety and efficacy of combined BRAF inhibition with vemurafenib and MEK inhibition with cobimetinib in patients with advanced BRAF-mutated melanoma. METHODS: We undertook a phase 1b study in patients with advanced BRAF(V600)-mutated melanoma. We included individuals who had either recently progressed on vemurafenib or never received a BRAF inhibitor. In the dose-escalation phase of our study, patients received vemurafenib 720 mg or 960 mg twice a day continuously and cobimetinib 60 mg, 80 mg, or 100 mg once a day for either 14 days on and 14 days off (14/14), 21 days on and 7 days off (21/7), or continuously (28/0). The primary endpoint was safety of the drug combination and to identify dose-limiting toxic effects and the maximum tolerated dose. Efficacy was a key secondary endpoint. All patients treated with vemurafenib and cobimetinib were included in safety and efficacy analyses (intention-to-treat). The study completed accrual and all analyses are final. This study is registered with ClinicalTrials.gov, number NCT01271803. FINDINGS: 129 patients were treated at ten dosing regimens combining vemurafenib and cobimetinib: 66 had recently progressed on vemurafenib and 63 had never received a BRAF inhibitor. Dose-limiting toxic effects arose in four patients. One patient on a schedule of vemurafenib 960 mg twice a day and cobimetinib 80 mg once a day 14/14 had grade 3 fatigue for more than 7 days; one patient on a schedule of vemurafenib 960 mg twice a day and cobimetinib 60 mg once a day 21/7 had a grade 3 prolongation of QTc; and two patients on a schedule of vemurafenib 960 mg twice a day and cobimetinib 60 mg 28/0 had dose-limiting toxic effects-one developed grade 3 stomatitis and fatigue and one developed arthralgia and myalgia. The maximum tolerated dose was established as vemurafenib 960 mg twice a day in combination with cobimetinib 60 mg 21/7. Across all dosing regimens, the most common adverse events were diarrhoea (83 patients, 64%), non-acneiform rash (77 patients, 60%), liver enzyme abnormalities (64 patients, 50%), fatigue (62 patients, 48%), nausea (58 patients, 45%), and photosensitivity (52 patients, 40%). Most adverse events were mild-to-moderate in severity. The most common grade 3 or 4 adverse events were cutaneous squamous-cell carcinoma (12 patients, 9%; all grade 3), raised amounts of alkaline phosphatase (11 patients, 9%]), and anaemia (nine patients, 7%). Confirmed objective responses were recorded in ten (15%) of 66 patients who had recently progressed on vemurafenib, with a median progression-free survival of 2·8 months (95% CI 2·6-3·4). Confirmed objective responses were noted in 55 (87%) of 63 patients who had never received a BRAF inhibitor, including six (10%) who had a complete response; median progression-free survival was 13·7 months (95% CI 10·1-17·5). INTERPRETATION: The combination of vemurafenib and cobimetinib was safe and tolerable when administered at the respective maximum tolerated doses. The combination has promising antitumour activity and further clinical development is warranted in patients with advanced BRAF(V600)-mutated melanoma, particularly in those who have never received a BRAF inhibitor; confirmatory clinical testing is ongoing. FUNDING: F Hoffmann-La Roche/Genentech.

Absolute bioavailability and effect of formulation change, food, or elevated pH with rabeprazole on cobimetinib absorption in healthy subjects.

Cobimetinib is a potent and highly selective inhibitor of MEK1/2. Since cobimetinib exhibited absorption variability in cancer patients, a series of single-dose studies in healthy subjects were conducted to determine absolute bioavailability and elucidate potential effects of formulation, food, and elevated gastric pH on cobimetinib bioavailability. Three crossover trials were performed with a 20 mg cobimetinib oral dose: absolute bioavailability using a 2 mg intravenous infusion (n = 13), relative bioavailability of tablets versus capsules and food effect (n = 20), and drug interaction with a proton pump inhibitor (20 mg of rabeprazole daily for 5 days prior to cobimetinib administration; n = 20). Absolute bioavailability of cobimetinib was 46.2% (24.2, CV %), likely due to metabolism rather than incomplete absorption. The mean systemic clearance of cobimetinib was low (11.7 L/h [28.2, CV %]). Administration of cobimetinib tablets with a high-fat meal delayed drug absorption (prolonged tmax) but had no statistically significant effect on cobimetinib exposure (Cmax and AUC0-∞). Tablet and capsule formulations of cobimetinib showed comparable exposures. Cobimetinib exhibited delayed absorption (tmax) in the presence of rabeprazole, with no statistically significant effects on drug exposure (Cmax and AUC0-∞) in the fasted state. In conclusion, cobimetinib oral absorption was not affected by change in formulation, food, or elevated gastric pH.

A phase II multicenter study of two different dosages of pemetrexed given in combination with cyclophosphamide as first-line treatment in patients with locally advanced or metastatic breast cancer.

Pemetrexed/cyclophosphamide was evaluated as first-line treatment for patients with locally advanced/metastatic breast cancer. In this randomized phase II study (NCT00190671), therapy consisted of either 600 mg/m(2) (P600) or 1,800 mg/m(2) (P1800) pemetrexed, followed by 600 mg/m(2) cyclophosphamide, every 21 days; 103 females (42 P600; 61 P1800) were enrolled. P600 was discontinued, as response rate (19.1%) was lower than targeted. In the P1800 arm, 20 patients had partial response (32.8%; 95% CI: 21.0-44.6) and 26 (42.6%) had stable disease. Median progression-free survival was 6.3 months (range: 0.3-31.1). P1800 plus cyclophosphamide 600 represents a regimen of reasonable efficacy and acceptable tolerability.

Time to Rethink the Current Paradigm for Assessing Kidney Function in Drug Development and Beyond.

Chronic kidney disease (CKD) is an important health issue that affects ~ 9.1% of the world adult population. Serum creatinine is the most commonly used biomarker for assessing kidney function and is utilized in different equations for estimating creatinine clearance or glomerular filtration rate (GFR). The Cockcroft-Gault formula for adults and "original" Schwartz formula for children have been the most commonly used equations for estimating kidney function during the last 3-4 decades. Introduction of standardized serum creatinine bioanalytical methodology has reduced interlaboratory variability but is not intended to be used with Cockcroft-Gault or original Schwartz equations. More accurate equations (for instance, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) for adults and bedside Schwartz or Chronic Kidney Disease in Children Schwartz equation for children) based on standardized serum creatinine values (and another biomarker-cystatin C) have been introduced and validated in recent years. Recently, the CKD-EPI equation refitted without a race variable was introduced. Clinical practice guidance in nephrology advocates a shift to these equations for managing health care of patients with CKD. The guidance also recommends use of albuminuria in addition to GFR for CKD diagnosis and management. Significant research with large data sets would be necessary to evaluate whether this paradigm would also be valuable in drug dose adjustments. This article attempts to highlight some important advancements in the field from a clinical pharmacology perspective and is a call to action to industry, regulators, and academia to rethink the current paradigm for assessing kidney function to enable dose recommendation in patients with CKD.

Assessment of cytochrome P450 3A4-mediated drug-drug interactions for ipatasertib using a fit-for-purpose physiologically based pharmacokinetic model.

PURPOSE: Ipatasertib, a potent and highly selective small-molecule inhibitor of AKT, is currently under investigation for treatment of cancer. Ipatasertib is a substrate and a time-dependent inhibitor of CYP3A4. It exhibits non-linear pharmacokinetics at subclinical doses in the clinical dose escalation study. To assess the DDI risk of ipatasertib at the intended clinical dose of 400 mg with CYP3A4 inhibitors, inducers, and substrates, a fit-for-purpose physiologically based pharmacokinetic (PBPK) model of ipatasertib was developed. METHODS: The PBPK model was constructed in Simcyp using in silico, in vitro, and clinical data and was optimized and verified using clinical data. RESULTS: The PBPK model described non-linear pharmacokinetics of ipatasertib and captured the magnitude of the observed clinical DDIs. Following repeated doses of 400 mg ipatasertib once daily (QD), the PBPK model predicted a 3.3-fold increase of ipatasertib exposure with itraconazole; a 2-2.5-fold increase with moderate CYP3A4 inhibitors, erythromycin and diltiazem; and no change with a weak CYP3A4 inhibitor, fluvoxamine. Additionally, in the presence of strong or moderate CYP3A4 inducers, rifampicin and efavirenz, ipatasertib exposures were predicted to decrease by 86% and 74%, respectively. As a perpetrator, the model predicted that ipatasertib (400 mg) caused a 1.7-fold increase in midazolam exposure. CONCLUSION: This study demonstrates the value of using a fit-for-purpose PBPK model to assess the clinical DDIs for ipatasertib and to provide dosing strategies for the concurrent use of other CYP3A4 perpetrators or victims.

Pharmacokinetics of Ipatasertib in Subjects With Hepatic Impairment Using 2 Methods of Classification of Hepatic Function.

Ipatasertib is a highly selective small-molecule pan-Akt inhibitor in clinical development. Ipatasertib is predominantly eliminated by the liver, and therefore, the effect of hepatic impairment on ipatasertib pharmacokinetics (PK) was evaluated. In this phase 1 open-label, parallel group study, the PK of ipatasertib were evaluated in subjects with hepatic impairment based on both the Child-Pugh and the National Cancer Institute Organ Dysfunction Working Group classification for hepatic impairment. A single dose of ipatasertib at 100 mg was administered and the PK was characterized in healthy subjects with normal hepatic function or mild, moderate, and severe hepatic impairment. Based on Child-Pugh classification, subjects with moderate and severe hepatic impairment had an ≈2- and 3-fold increase in systemic exposure (area under the plasma concentration-time curve from time 0 to infinity [AUC0-∞ ]) to ipatasertib, respectively, compared to subjects with normal hepatic function. Systemic exposure (AUC0-∞ ) to ipatasertib in subjects with mild hepatic impairment was comparable to that in subjects with normal hepatic function. In accordance with reduced clearance capacity, subjects with mild to severe hepatic impairment showed lower systemic exposure (AUC0-∞ ) of ipatasertib metabolite M1 (G-037720). Overall results were comparable between Child-Pugh and National Cancer Institute Organ Dysfunction Working Group classification criteria. Based on the results from this study, no dosage adjustment is required for ipatasertib when treating patients with mild hepatic impairment, whereas a dose reduction would be recommended for subjects with moderate or severe hepatic impairment. Based on real-world data analysis, ≈2% of the intended patient population is expected to need a modified dose due to moderate or severe hepatic impairment.

Cobimetinib in Pediatric and Young Adult Patients with Relapsed or Refractory Solid Tumors (iMATRIX-cobi): A Multicenter, Phase I/II Study.

BACKGROUND: The MAPK pathway is an emerging target across a number of adult and pediatric tumors. Targeting the downstream effector of MAPK, MEK1, is a proposed strategy to control the growth of MAPK-dependent tumors. OBJECTIVE: iMATRIX-cobi assessed the safety, pharmacokinetics, and anti-tumor activity of cobimetinib, a highly selective MEK inhibitor, in children and young adults with relapsed/refractory solid tumors. PATIENTS AND METHODS: This multicenter Phase I/II study enrolled patients aged 6 months to < 30 years with solid tumors with known/expected MAPK pathway involvement. Patients received cobimetinib tablet or suspension formulation on Days 1-21 of a 28-day cycle. Dose escalation followed a rolling 6 design. The primary endpoint was safety; secondary endpoints were pharmacokinetics and anti-tumor activity. RESULTS: Of 56 enrolled patients (median age 9 years [range 3-29]), 18 received cobimetinib tablets and 38 cobimetinib suspension. Most common diagnoses were low-grade glioma (LGG; n = 32, including n = 12 in the expansion cohort) and plexiform neurofibroma within neurofibromatosis type 1 (n = 12). Six patients (11 %) experienced dose-limiting toxicities (including five ocular toxicity events), which established a pediatric recommended Phase II dose (RP2D) of 0.8 mg/kg tablet and 1.0 mg/kg suspension. Most frequently reported treatment-related adverse events were gastrointestinal and skin disorders. Steady state mean exposure (Cmax, AUC0-24) of cobimetinib at the RP2D (1.0 mg/kg suspension) was ~ 50 % lower than in adults receiving the approved 60 mg/day dose. Overall response rate was 5.4 % (3/56; all partial responses in patients with LGG). CONCLUSIONS: The safety profile of cobimetinib in pediatrics was similar to that reported in adults. Clinical activity was observed in LGG patients with known/suspected MAPK pathway activation. Cobimetinib combination regimens may be required to improve response rates in this pediatric population. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT02639546, registered December 24, 2015.

Single- and multiple-dose pharmacokinetics, potential for CYP3A inhibition, and food effect in patients with cancer and healthy subjects receiving ipatasertib.

PURPOSE: To examine the single- and multiple-dose pharmacokinetics (PK), CYP3A inhibition potential of ipatasertib, and effect of food on PK of ipatasertib in patients with refractory solid tumors and a dedicated food effect assessment in healthy subjects. METHODS: The Phase I dose-escalation study enrolled patients with solid tumors in a standard 3 + 3 design with a 1 week washout after the first dose, followed by once-daily dosing on a 3-week-on/1-week-off schedule. In the expansion cohort, the effect of ipatasertib on CYP3A substrate (midazolam) was assessed by examining the change in midazolam exposure when dosed in the absence and presence of steady-state ipatasertib at 600 mg. The effect of food on ipatasertib PK was studied with ipatasertib administered in fed or fasted state (6 patients from Phase I patient study and 18 healthy subjects from the dedicated food effect study). RESULTS: Ipatasertib was generally well tolerated at doses up to 600 mg given daily for 21 days. Ipatasertib showed rapid absorption (tmax, 0.5-3 h), was dose-proportional over a range of 200-800 mg, had a median half-life (range) of 45.0 h (27.8-66.9 h), and had approximately two-fold accumulation following once-daily dosing. Midazolam exposure (AUC0-∞) increased by 2.2-fold in the presence of ipatasertib. PK was comparable in subjects administered ipatasertib in a fed or fasted state. CONCLUSION: Ipatasertib exhibited rapid absorption and was dose-proportional over a broad dose range. Ipatasertib appeared to be a moderate CYP3A inhibitor when administered at 600 mg and could be administered with or without food in clinical studies. TRAIL REGISTRATION: NCT01090960 (registered March 23, 2010); NCT02536391 (registered August 31, 2015).

Effect of Hepatic Impairment on Cobimetinib Pharmacokinetics: The Complex Interplay Between Physiological Changes and Drug Characteristics.

Cobimetinib is a kinase inhibitor indicated for use in combination with vemurafenib for treatment of unresectable/metastatic melanoma with specific BRAF mutations. Cobimetinib is extensively metabolized in liver; thus, patients with hepatic impairment (HI) might have increased cobimetinib exposure. In this study, we investigated the impact of HI on the pharmacokinetics (PK) and safety of cobimetinib. Subjects with normal hepatic function and mild to severe HI were enrolled. All subjects received a single oral dose of 10 mg cobimetinib, and serial blood samples were collected at specified times. Cobimetinib PK in subjects with mild and moderate HI was similar to that in those with normal liver function. However, subjects with severe HI, on average, showed ∼30% lower total AUC0-∞ and ∼2-fold higher unbound AUC0-∞ compared with those with normal hepatic function. These exposure differences can be explained by lower albumin levels observed in subjects with severe HI, the strong correlation between albumin level and the unbound fraction and the general PK variability of cobimetinib. In addition, previous studies with cobimetinib showed a lack of an exposure-response relationship for efficacy and safety. Therefore, collectively, our results suggest that the starting dose for patients with hepatic impairment can be the same as that for those with normal hepatic function.

Phase I and pharmacokinetic study of pemetrexed plus cisplatin in chemonaive patients with locally advanced or metastatic malignant pleural mesothelioma or non-small cell lung cancer.

PURPOSE: Pemetrexed is approved as monotherapy and in combination with cisplatin. The established combination dose was identified before the addition of folic acid and vitamin B(12) to the treatment regimen. We evaluated the toxicity and pharmacokinetics (PK) of higher pemetrexed doses with cisplatin and vitamin supplementation. EXPERIMENTAL DESIGN: Patients with malignant pleural mesothelioma or non-small cell lung cancer received pemetrexed doses from 500 to 900 mg/m(2) + 75 mg/m(2) cisplatin once every 21 days. Folic acid and vitamin B(12) were administered per label recommendations. RESULTS: Twenty-one patients received a combined total of 84 cycles. The maximum tolerated dose was 900 mg/m(2) pemetrexed + 75 mg/m(2) cisplatin. Dose-limiting toxicities at this dose included grade 3 anemia, bronchopneumonia, and neutropenia, and 1 death from sepsis secondary to grade 4 febrile neutropenia, considered possibly related to study drugs. The recommended dose was 800 mg/m(2) pemetrexed + 75 mg/m(2) cisplatin. Pemetrexed PK were consistent across doses; pemetrexed did not seem to affect total or free platinum PK. CONCLUSIONS: Pemetrexed with vitamin supplementation was safe and well tolerated at higher doses than the currently established 500 mg/m(2) + 75 mg/m(2) cisplatin. Based on this study, the recommended dose would be 800 mg/m(2) pemetrexed + 75 mg/m(2) cisplatin. However, recent studies showed a lack of improved efficacy for 900 or 1,000 mg/m(2) single-agent pemetrexed versus 500 mg/m(2) and a lack of PK/pharmacodynamic exposure-response relationship for the pemetrexed/cisplatin combination across pemetrexed exposures corresponding to this dose range. Based on currently available evidence, we recommend retaining the established dose.