Study of Cobimetinib in Participants With Solid Tumors

Study Overview
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Brief Summary
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This non-randomized, open-label, study will determine the highest safe dose of cobimetinib, how often it should be taken, how well participants with cancer tolerate cobimetinib and will assess the pharmacokinetic effect of midazolam and dextromethorphan on the study drug.

Official Title
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A Phase 1 Dose-Escalation Study of the Safety and Pharmacokinetics of GDC-0973/XL518 Administered Orally Daily to Subjects With Solid Tumors

Conditions
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Solid Tumor

Intervention / Treatment
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* Drug: cobimetinib
* Drug: dextromethorphan
* Drug: midazolam


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Histologically confirmed solid tumor that is metastatic or unresectable, and for which standard curative or palliative measures do not exist or are no longer effective, and there are no known therapies to prolong survival Disease that is measurable according to Response Evaluation Criteria in Solid Tumors (RECIST) Adequate organ and marrow function Sexually active participants must use medically acceptable methods of contraception during the course of the study and at least 11 days after the last dose of study treatment Female participants of childbearing potential must have a negative serum pregnancy test at screening No other history of/or ongoing malignancy that would potentially interfere with the interpretation of the pharmacodynamic or efficacy assays Exclusion Criteria: Anticancer treatment (e.g., chemotherapy, radiotherapy, cytokines, or hormones) within 28 days (6 weeks for nitrosoureas or mitomycin C, or 14 days for hormonal therapy or kinase inhibitors) before the first dose of study drug The participant has not recovered to Grade </=1 from adverse events (AEs) or to within 10% of baseline values due to investigational or other agents administered more than 28 days prior to study enrollment The participant has received another investigational agent within 28 days of the first dose of study drug Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, diabetes, symptomatic congestive heart failure, unstable angina pectoris, or cardiac arrhythmia The participant is pregnant or breastfeeding The participant is known to be positive for the human immunodeficiency virus (HIV) Allergy or hypersensitivity to components of the cobimetinib formulation

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Stage 1: Cobimetinib Dose Escalation (21/7 Schedule)<br>Participants will receive cobimetinib (GDC-0973/XL518) at the starting dose of 0.05 mg/kg via solution or capsule, once daily for Days 1-21 of each 28-day cycle (21 days on drug followed by 7 days off treatment [21/7 schedule]). Treatment will continue until progressive disease (PD) or unacceptable toxicity for up to 1 year at the discretion of investigator and beyond 1 year with the agreement of the sponsor. | Drug: cobimetinib<br>* Repeating oral dose<br>* Other names: GDC-0973/XL518;|
| Experimental: Stage 1A: Cobimetinib Dose Escalation (14/14 Schedule)<br>Participants will receive cobimetinib at the starting dose of 60 mg via solution or capsule, once daily for Days 1-14 of each 28-day cycle (14 days on drug followed by 14 days off treatment [14/14 schedule]). Treatment will continue until progressive disease (PD) or unacceptable toxicity for up to 1 year at the discretion of investigator and beyond 1 year with the agreement of the sponsor. | Drug: cobimetinib<br>* Repeating oral dose<br>* Other names: GDC-0973/XL518;|
| Experimental: Stage 2: Cobimetinib Expansion (21/7 Schedule)<br>Participants will receive cobimetinib at the maximum tolerated dose (MTD) established in Stage 1, once daily for Days 1-21 of each 28-day cycle (21 days on drug followed by 7 days off treatment [21/7 schedule]). Treatment will continue until progressive disease (PD) or unacceptable toxicity for up to 1 year at the discretion of investigator and beyond 1 year with the agreement of the sponsor. | Drug: cobimetinib<br>* Repeating oral dose<br>* Other names: GDC-0973/XL518;|
| Experimental: Stage 2 A: Cobimetinib Expansion (14/14 Schedule)<br>Participants will receive cobimetinib at the MTD established in Stage 1A, once daily for Days 1-14 of each 28-day cycle (14 days on drug followed by 14 days off treatment [14/14 schedule]). Treatment will continue until progressive disease (PD) or unacceptable toxicity for up to 1 year at the discretion of investigator and beyond 1 year with the agreement of the sponsor. | Drug: cobimetinib<br>* Repeating oral dose<br>* Other names: GDC-0973/XL518;|
| Experimental: Stage 3: Cobimetinib+Midazolam+Dextromethorphan<br>Participants will receive a single dose of midazolam (2 mg of midazolam syrup) and dextromethorphan (30 mg tablet) on Cycle 1 Day 1, in the absence of cobimetinib. After a 2-day washout period, participants will receive 21 consecutive daily doses of cobimetinib (60-mg) followed by a 7-day washout period. Participants will receive another single dose of midazolam and dextromethorphan on Cycle 1 Day 15, in the presence of steady-state cobimetinib concentrations. In Cycle 2 and beyond participants will receive cobimetinib alone, administered as a 60-mg daily dose for 21 consecutive days in 28-day cycles (21/7 schedule). | Drug: cobimetinib<br>* Repeating oral dose<br>* Other names: GDC-0973/XL518;Drug: dextromethorphan<br>* In Stage III only: single dose of dextromethorphan<br>Drug: midazolam<br>* In Stage III only: single dose of midazolam<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Stage 1 and 1A: Number of Participants With Dose Limiting Toxicities (DLTs) | Adverse events (AE) were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) v3.0. DLT was defined as either of the following occurring during the Study Treatment Period. The occurrence of a drug-related AE that, in the opinion of the cohort review committee (CRC), was of potential clinical significance such that further dose escalation would expose participants in higher dose cohorts to risk of irreversible medical harm or require medical treatment to avoid irreversible medical harm or non-hematologic toxicity Grade 3 or 4 events, including Grade 3 nausea and/or vomiting and/or Grade 3 diarrhea, despite prophylaxis and/or treatment Hematologic toxicity Grade 4 thrombocytopenia Grade 4 neutropenia of greater than or equal to (≥) 4 days' duration Grade 4 neutropenia of any duration with fever or documented infection | Stage 1 and 1A: Days 1 to 28 of Cycle 1 | 
| Stage 1: Maximum Tolerated Dose (MTD) of Cobimetinib in 21/7 Schedule | AEs were graded according to the NCI-CTCAE v3.0. A DLT was determined from clinical findings during the Study Treatment Period (Cycle 1, Days 1). MTD was defined as the dose at which no DLTs were observed. DLT was defined as either of the following occurring during the Study Treatment Period. The occurrence of a drug-related AE that, in the opinion of the CRC, was of potential clinical significance such that further dose escalation would expose participants in higher dose cohorts to risk of irreversible medical harm or require medical treatment to avoid irreversible medical harm or non-hematologic toxicity Grade 3 or 4 events, including Grade 3 nausea and/or vomiting and/or Grade 3 diarrhea, despite prophylaxis and/or treatment Hematologic toxicity Grade 4 thrombocytopenia Grade 4 neutropenia of greater than or equal to (≥) 4 days' duration Grade 4 neutropenia of any duration with fever or documented infection | Stage 1: Days 1 to 28 of Cycle 1 | 
| Stage 1A: MTD of Cobimetinib in 14/14 Schedule | AEs were graded according to NCI-CTCAE v3.0. A DLT was the basis for determining MTD in Stage 1A participants. The participants of Stage 1A are dose-escalation cohorts, starting at the MTD of the 21/7 schedule, were treated on a 14/14 schedule to determine the MTD. A DLT was defined as either of the following occurring during the Study Treatment Period: Occurrence of a drug-related AE that, in the opinion of the CRC, was of potential clinical significance such that further dose escalation would expose participants to risk of irreversible medical harm; Nonhematologic toxicity: Grade 3 or 4 events, including Grade 3 nausea and/or vomiting and/or Grade 3 diarrhea, despite prophylaxis and/or treatment; Hematologic toxicity: Grade 4 thrombocytopenia. Grade 4 neutropenia of more than 4 days' duration; Grade 4 neutropenia of any duration with fever or documented infection. AEs (Grade 3 or higher) for which a clinical cause unrelated to cobimetinib was evident was not considered DLTs. | Stage 1A: Days 1 to 28 of Cycle 1 | 
| Stage 1: Maximum Observed Concentration (Cmax) of Cobimetinib at Day 1, Cycle 1 | Cmax is defined as the maximum plasma concentration achieved after administration of cobimetinib on Day 1, Cycle 1 in Stage 1 and was measured as nanograms per milliliter (ng/mL). | Stage 1: Pre-dose and 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 1 and pre-dose on Cycle 1 Day 2 | 
| Stage 1: Area Under the Plasma Cobimetinib Concentration Curve From Time 0 to 24 Hours (AUC 0-24) Day 1, Cycle 1 | The area under the concentrations-time curve (AUC0-24) was calculated with the measured data points from the time of administration of cobimetinib up to 24 h after administration by the trapezoidal formula. AUC 0-24 is the truncated AUC over a 24-hour sampling interval. The concentration-time curve is the result of time points of blood sampling and its measured concentration of free cobimetinib in the blood samples. AUC is measured as hours times nanograms per milliliter (h*ng/mL). | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 1, pre-dose on Cycle 1 Day 2 | 
| Stage 1: Time to Maximum Concentration (Tmax) of Cobimetinib at Day 1, Cycle 1 | Tmax is defined as the time to reach Cmax during stage 1 at Day 1 Cycle 1. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 1 and pre-dose on Cycle 1 Day 2 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Stage 1: Tmax of Cobimetinib at Steady State | Tmax is defined as the time to reach Cmax during stage 1 in steady state. Steady state was reached when overall intake of cobimetinib was in dynamic equilibrium with its elimination. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 21, 24, 48, and 72 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22, 23, and 24, respectively) | 
| Stage 1: AUC 0-24 of Cobimetinib at Steady State | The area under the AUC0-24 for steady state in stage 1 was calculated with the measured data points from the time of administration of cobimetinib up to 24 h after administration by the trapezoidal formula. AUC 0-24 is the truncated AUC over a 24-hour sampling interval. The concentration-time curve is the result of time points of blood sampling and its measured concentration of free cobimetinib in the blood samplings. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 21, 24, 48, and 72 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22, 23, and 24, respectively) | 
| Stage 1: AUC 0-24/D of Cobimetinib at Steady State | AUC 0-24/D is the dose normalized truncated AUC over a 24-hour sampling interval. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 21, 24, 48, and 72 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22, 23, and 24, respectively) | 
| Stage 1: Accumulation Ratio of Cobimetinib at Steady State | Accumulation Ratio: AUC0-24 at steady state divided by AUC0-24 on Cycle 1 Day 1. It was calculated only for participants who had a quantifiable AUC 0-24 at steady state. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 1, Day 21, 24, 48, and 72 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22, 23, and 24, respectively) | 
| Stage 1: Apparent Clearance of Cobimetinib at Steady State | Clearance of a drug is a measure of the rate at which a drug is metabolized or eliminated by normal biological processes. Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the blood. Apparent clearance was calculated only for participants who had a quantifiable AUC 0-24 in steady state. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 21, 24, 48, and 72 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22, 23, and 24, respectively) | 
| Stage 1: Half-Life (t1/2) of Cobimetinib at Steady State | t1/2 is the half-life of cobimetinib measured over the terminal phase by noncompartmental analysis in stage 1 in steady state. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 21, 24, 48, and 72 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22, 23, and 24, respectively) | 
| Stage 1: Cmax of Cobimetinib at Steady State | Cmax is defined as the maximum plasma concentration achieved after administration of cobimetinib in Stage 1 and was measured at steady state in ng/mL. | Stage 1: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12-18 hours post-dose on Cycle 1 Day 21, 24, 48, and 72 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22, 23, and 24, respectively) | 
| Stage 1A: Tmax of Cobimetinib at Cycle 1 Day 1 | Tmax is defined as the time to reach Cmax during stage 1A at Day 1. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 1, pre-dose on Cycle 1 Day 2 | 
| Stage 1A: Cmax of Cobimetinib at Cycle 1 Day 1 | Cmax is defined as the maximum plasma concentration achieved after administration of cobimetinib on on Day 1 in Stage 1A and was measured as ng/mL. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 1, pre-dose on Cycle 1 Day 2 | 
| Stage 1A: AUC 0-24 of Cobimetinib at Cycle 1 Day 1 | AUC0-24 for stage 1A was calculated on Day 1 with the measured data points from the time of administration of cobimetinib up to 24 h after administration by the trapezoidal formula. AUC 0-24 is the truncated AUC over a 24-hour sampling interval. The concentration-time curve is the result of time points of blood sampling and its measured concentration of free cobimetinib in the blood samplings. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 1, pre-dose on Cycle 1 Day 2 | 
| Stage 1A: t1/2 of Cobimetinib at Steady State | t1/2 is the half-life of cobimetinib measured over the terminal phase by noncompartmental analysis in stage 1A in steady state. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24, 48, 72 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15, 16, and 17, respectively) | 
| Stage 1A: Tmax of Cobimetinib at Steady State | Tmax is defined as the time to reach Cmax during stage 1A in steady state. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24, 48, 72 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15, 16, and 17, respectively) | 
| Stage 1A: Apparent Clearance of Cobimetinib at Steady State | Clearance of a drug is a measure of the rate at which a drug is metabolized or eliminated by normal biological processes. Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the blood. Apparent clearance was calculated only for participants who had a quantifiable AUC 0-24 in steady state. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24, 48, 72 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15, 16, and 17, respectively) | 
| Stage 1A: Accumulation Ratio of Cobimetinib at Steady State | Accumulation Ratio: AUC0-24 at steady state divided by AUC0-24 on Cycle 1 Day 1. It was calculated only for participants who had a quantifiable AUC 0-24 at steady state. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 1, 14, 24, 48, 72 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15, 16, and 17, respectively) | 
| Stage 1A: AUC 0-24 of Cobimetinib at Steady State | The area under the AUC0-24 for steady state in stage 1A was calculated with the measured data points from the time of administration of cobimetinib up to 24 h after administration by the trapezoidal formula. AUC 0-24 is the truncated AUC over a 24-hour sampling interval. The concentration-time curve is the result of time points of blood sampling and its measured concentration of free cobimetinib in the blood samplings. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24, 48, 72 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15, 16, and 17, respectively) | 
| Stage 1A: AUC 0-24/D of Cobimetinib at Steady State | AUC 0-24/D is the dose normalized truncated AUC over a 24-hour sampling interval. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24, 48, 72 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15, 16, and 17, respectively) | 
| Stage 1A: Cmax of Cobimetinib at Steady State | Cmax is defined as the maximum plasma concentration achieved after administration of cobimetinib in Stage 1A and was measured in steady state as ng/mL. | Stage 1A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24, 48, 72 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15, 16, and 17, respectively) | 
| Stage 2: Cmax of Cobimetinib at Cycle 1 Day 1 | Cmax is defined as the maximum plasma concentration achieved after administration of cobimetinib in Stage 2 and was measured in ng/mL. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 1, pre-dose on Cycle 1 Day 2 | 
| Stage 2:AUC 0-24 of Cobimetinib at Cycle 1 Day 1 | The area under the AUC0-24 on Day 1 in stage 2 was calculated with the measured data points from the time of administration of cobimetinib up to 24 h after administration by the trapezoidal formula. AUC 0-24 is the truncated AUC over a 24-hour sampling interval. The concentration-time curve is the result of time points of blood sampling and its measured concentration of free cobimetinib in the blood samplings. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 1, pre-dose on Cycle 1 Day 2 | 
| Stage 2: Tmax of Cobimetinib at Cycle 1 Day 1 | Tmax is defined as the time to reach Cmax during stage 2 on Day 1. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 1, pre-dose on Cycle 1 Day 2 | 
| Stage 2: Tmax of Cobimetinib at Steady State | Tmax is defined as the time to reach Cmax during stage 2 in steady state. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 21, 24 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22), and between Cycle 1 Days 26-28 | 
| Stage 2: AUC 0-24 of Cobimetinib at Steady State | The area under the AUC0-24 for steady state in stage 2 was calculated with the measured data points from the time of administration of cobimetinib up to 24 h after administration by the trapezoidal formula. AUC 0-24 is the truncated AUC over a 24-hour sampling interval. The concentration-time curve is the result of time points of blood sampling and its measured concentration of free cobimetinib in the blood samplings. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 21, 24 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22), and between Cycle 1 Days 26-28 | 
| Stage 2: AUC 0-24/D of Cobimetinib at Steady State | AUC 0-24/D is the dose normalized truncated AUC over a 24-hour sampling interval. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 21, 24 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22), and between Cycle 1 Days 26-28 | 
| Stage 2: Accumulation Ratio of Cobimetinib at Steady State | Accumulation ratio is AUC0-24 at steady state divided by AUC0-24 on Cycle 1 Day 1. It was calculated only for participants who had a quantifiable AUC 0-24 at steady state. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 21, 24 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22), and between Cycle 1 Days 26-28 | 
| Stage 2: Apparent Clearance of Cobimetinib at Steady State | Clearance of a drug is a measure of the rate at which a drug is metabolized or eliminated by normal biological processes. Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the blood. Apparent clearance was calculated only for participants who had a quantifiable AUC 0-24 in steady state. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 21, 24 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22), and between Cycle 1 Days 26-28 | 
| Stage 2:Half-Life of Cobimetinib at Steady State | T1/2 half-life of cobimetinib measured over the terminal phase by noncompartmental analysis. | Stage 2: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 21, 24 hours post Cycle 1 Day 21 dose (Cycle 1 Day 22), and between Cycle 1 Days 26-28 | 
| Stage 2A: AUC 0-24/D of Cobimetinib at Steady State | AUC 0-24/D is the dose normalized truncated AUC over a 24-hour sampling interval. | Stage 2A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15), and between Cycle 1 Days 26-28 | 
| Stage 2A: Accumulation Ratio of Cobimetinib at Steady State | Accumulation Ratio AUC0-24 is ratio of AUC on Day 20: Day 1. | Stage 2A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15), and between Cycle 1 Days 26-28 | 
| Stage 2A: Apparent Clearance of Cobimetinib at Steady State | Apparent clearance is the plasma clearance of absorbed drug. | Stage 2A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15), and between Cycle 1 Days 26-28 | 
| Stage 2A: Half-Life of Cobimetinib at Steady State |  | Stage 2A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15), and between Cycle 1 Days 26-28 | 
| Stage 2A: Tmax of Cobimetinib at Steady State | Tmax is defined as the time to reach Cmax during stage 2A in steady state. | Stage 2A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15), and between Cycle 1 Days 26-28 | 
| Stage 2A: Cmax of Cobimetinib at Steady State | Cmax is the maximum plasma concentration achieved following the Day 20 dose in Stage 2A. | Stage 2A: Pre-dose & 0.5, 1, 1.5, 2, 3, 4, 6 hours post-dose on Cycle 1 Day 14, 24 hours post Cycle 1 Day 14 dose (Cycle 1 Day 15), and between Cycle 1 Days 26-28 | 
| Stage III: Cmax of Dextromethorphan | Cmax is defined as maximum observed plasma concentration and was determined both in the presence (Cycle 1 Day 15) and absence of cobimetinib (Cycle 1 Day 1). | Stage III: Predose, 0.5, 1, 1.5, 2, 4, 6, 8, and 24 hours after dextromethorphan administration on Days 1 and 15 of Cycle 1 | 
| Stage III: AUC 0-24 of Dextromethorphan | AUC0-24 is the area under the plasma drug concentration curve over a 24-hour sampling interval and was determined both in presence (Cycle 1 Day 15) and absence (Cycle 1 Day 1) of cobimetinib. | Stage III: Predose, 0.5, 1, 1.5, 2, 4, 6, 8, and 24 hours after dextromethorphan administration on Days 1 and 15 of Cycle 1 | 
| Stage III: AUC 0-inf of Dextromethorphan | AUC0-inf is AUC from time 0 to infinity and was calculated both in presence Cycle 1 Day 15) and absence (Cycle 1 Day 1) of cobimetinib. | Stage III: Predose, 0.5, 1, 1.5, 2, 4, 6, 8, and 24 hours after dextromethorphan administration on Days 1 and 15 of Cycle 1 | 
| Stage III: Cmax of Midazolam | Cmax is the maximum observed plasma concentration and was calculated both in the presence (Cycle 1 Day 15) and absence (Cycle 1 Day 1) of cobimetinib. | Stage III: Predose, 0.5, 1, 1.5, 2, 4, 6, 8, and 24 hours after dextromethorphan administration on Days 1 and 15 of Cycle 1 | 
| Stage III: AUC0-24 of Midazolam | AUC0-24 is the area under the plasma drug concentration curve over a 24-hour sampling interval and was calculated both in the presence (Cycle 1 Day 15) and absence (CXycle 1 Day 1) of cobimetinib. | Stage III: Predose, 0.5, 1, 1.5, 2, 4, 6, 8, and 24 hours after dextromethorphan administration on Days 1 and 15 of Cycle 1 | 
| Stage III: AUC0-inf of Midazolam | AUC0-inf is the AUC from time 0 to infinity and was calculated both in the presence (Cycle 1 Day 15) and absence (Cycle 1 Day 1) of cobimetinib. | Stage III: Predose, 0.5, 1, 1.5, 2, 4, 6, 8, and 24 hours after dextromethorphan administration on Days 1 and 15 of Cycle 1 |