Participants of Cohort 1 will receive placebo matched to GDC-0853, orally once daily along with adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants will remain on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week are allowed only if there is clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigator's discretion.

Participants of Cohort 1 will receive placebo matched to GDC-0853, orally once daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants will remain on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week are allowed only if there is clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigator's discretion.

Participants of Cohort 2 will receive GDC-0853 high dose, orally twice daily for 12 weeks. Participants will remain on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week are allowed only if there is clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigator's discretion.

Participants of Cohort 2 will receive placebo matched to GDC-0853, orally twice daily for 12 weeks. Participants will remain on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week are allowed only if there is clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigator's discretion.

Participants will receive adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks.

Participants will receive stable background therapy of folic acid of at least 5 mg total dose weekly (or equivalent) as per investigator's discretion.

Participants will receive stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week are allowed only if there is clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines).

Participants will receive placebo matched to adalimumab, subcutaneously Q2W and/or placebo matched to GDC-0853, orally once or twice daily for 12 weeks in Cohort 1 or 2.

ACR50 response is defined as a ≥ 50% improvement (reduction) compared with baseline for both total joint count-68 joints (TJC68) and swollen joint count-66 joints (SJC66), as well as for three of the additional five ACR core set variables: Patient's Assessment of Pain over the previous 24 hours: using a Visual Analog Scale (VAS) left end of the line 0=no pain to right end of the line 100=unbearable pain; Patient's Global Assessment of Disease Activity and Physician's Global Assessment of Disease Activity over the previous 24 hours using a VAS where left end of the line 0=no disease activity to right end of the line 100=maximum disease activity; Health Assessment Questionnaire: 20 questions, 8 components: dressing/grooming, arising, eating, walking, hygiene, reach, grip and activities, 0=without difficulty to 3=unable to do; and acute-phase reactant [either C-reactive protein or Erythrocyte Sedimentation Rate].

ACR20 response is defined as a ≥ 20% improvement (reduction) compared with baseline for both total joint count-68 joints (TJC68) and swollen joint count-66 joints (SJC66), as well as for three of the additional five ACR core set variables: Patient's Assessment of Pain over the previous 24 hours: using a Visual Analog Scale (VAS) left end of the line 0=no pain to right end of the line 100=unbearable pain; Patient's Global Assessment of Disease Activity and Physician's Global Assessment of Disease Activity over the previous 24 hours using a VAS where left end of the line 0=no disease activity to right end of the line 100=maximum disease activity; Health Assessment Questionnaire: 20 questions, 8 components: dressing/grooming, arising, eating, walking, hygiene, reach, grip and activities, 0=without difficulty to 3=unable to do; and acute-phase reactant [either C-reactive protein or Erythrocyte Sedimentation Rate]

ACR50 response is defined as a ≥ 50% improvement (reduction) compared with baseline for both total joint count-68 joints (TJC68) and swollen joint count-66 joints (SJC66), as well as for three of the additional five ACR core set variables: Patient's Assessment of Pain over the previous 24 hours: using a Visual Analog Scale (VAS) left end of the line 0=no pain to right end of the line 100=unbearable pain; Patient's Global Assessment of Disease Activity and Physician's Global Assessment of Disease Activity over the previous 24 hours using a VAS where left end of the line 0=no disease activity to right end of the line 100=maximum disease activity; Health Assessment Questionnaire: 20 questions, 8 components: dressing/grooming, arising, eating, walking, hygiene, reach, grip and activities, 0=without difficulty to 3=unable to do; and acute-phase reactant [either C-reactive protein or Erythrocyte Sedimentation Rate].

ACR70 response is defined as a ≥ 70% improvement (reduction) compared with Baseline for both total joint count-68 joints (TJC68) and swollen joint count-66 joints (SJC66), as well as for three of the additional five ACR core set variables: Patient's Assessment of Pain over the previous 24 hours: using a Visual Analog Scale (VAS) left end of the line 0=no pain to right end of the line 100=unbearable pain; Patient's Global Assessment of Disease Activity and Physician's Global Assessment of Disease Activity over the previous 24 hours using a VAS where left end of the line 0=no disease activity to right end of the line 100=maximum disease activity; Health Assessment Questionnaire: 20 questions, 8 components: dressing/grooming, arising, eating, walking, hygiene, reach, grip and activities, 0=without difficulty to 3=unable to do; and acute-phase reactant [either C-reactive protein or Erythrocyte Sedimentation Rate].

The DAS28 score is a measure of the patient's disease activity calculated using the tender joint count (TJC) [28 joints], swollen joint count (SJC) [28 joints], patient's global assessment of disease activity [visual analog scale: 0=no disease activity to 100=maximum disease activity] and the erythrocyte sedimentation rate (ESR) for a total possible score of 0 to approximately 10. Scores below 2.6 indicate best disease control and scores above 5.1 indicate worse disease control. DAS28 Remission is defined as a DAS28 score < 2.6.

The DAS28 score is a measure of the patient's disease activity calculated using the tender joint count (TJC) [28 joints], swollen joint count (SJC) [28 joints], patient's global assessment of disease activity [visual analog scale: 0=no disease activity to 100=maximum disease activity] and the erythrocyte sedimentation rate (ESR) for a total possible score of 0 to approximately 10. Scores below 2.6 indicate best disease control and scores above 5.1 indicate worse disease control. DAS28 Remission is defined as a DAS28 score < 2.6.

The DAS28 score is a measure of the patient's disease activity calculated using the tender joint count (TJC) [28 joints], swollen joint count (SJC) [28 joints], patient's global assessment of disease activity [visual analog scale: 0=no disease activity to 100=maximum disease activity] and the erythrocyte sedimentation rate (ESR) for a total possible score of 0 to approximately 10. Scores below 2.6 indicate best disease control and scores above 5.1 indicate worse disease control. DAS28 Remission is defined as a DAS28 score < 2.6.

The DAS28 score is a measure of the patient's disease activity calculated using the tender joint count (TJC) [28 joints], swollen joint count (SJC) [28 joints], patient's global assessment of disease activity [visual analog scale: 0=no disease activity to 100=maximum disease activity] and the erythrocyte sedimentation rate (ESR) for a total possible score of 0 to approximately 10. Scores below 2.6 indicate best disease control and scores above 5.1 indicate worse disease control. DAS28 Remission is defined as a DAS28 score < 2.6.

The DAS28 score is a measure of the patient's disease activity calculated using the tender joint count (TJC) [28 joints], swollen joint count (SJC) [28 joints], patient's global assessment of disease activity [visual analog scale: 0=no disease activity to 100=maximum disease activity] and the erythrocyte sedimentation rate (ESR) for a total possible score of 0 to approximately 10. Scores below 2.6 indicate best disease control and scores above 5.1 indicate worse disease control. LDAS is defined as DAS28 ≤ 3.2

The DAS28 score is a measure of the patient's disease activity calculated using the tender joint count (TJC) [28 joints], swollen joint count (SJC) [28 joints], patient's global assessment of disease activity [visual analog scale: 0=no disease activity to 100=maximum disease activity] and the erythrocyte sedimentation rate (ESR) for a total possible score of 0 to approximately 10. Scores below 2.6 indicate best disease control and scores above 5.1 indicate worse disease control. DAS28 Remission is defined as a DAS28 score < 2.6

Boolean Remission is defined as Tender joint count less than 1, Swollen joint count less than 1, CRP less than 1 mg/dL, patient global assessment less than 1 (on 0 to 10 VAS scale).

CDAI was derived as the sum of the following: tender joint count (TJC), swollen joint count (SJC), participant global assessment (PGA) of disease activity, and physician assessment of disease activity. TJC and SJC were taken as the number of tender and swollen joints, respectively, out of 28 assessed joints. PGA and physician assessment of disease activity were scored 0-100 millimeters (mm) and rounded to the nearest centimeter (cm) on a visual analog scale (VAS), where higher scores indicate greater perceived disease activity. The total CDAI score range was 0-76, where higher scores indicate increased disease activity. Change from baseline at a particular time point was calculated among patients with data available at both baseline and the time point of interest. Negative values indicate improvement/reduction in RA disease activity.

Clinical Disease Activity Index is defined as CDAI= : SJC(28) + TJC(28) + PGA + MDG where TJC and SJC are the tender and swollen joint counts from 28 joints, PGA is the patient's global assessment of disease activity (on a 0-10 scale) and MDG is physician global assessment of disease activity (on a 0-10 scale). The cutoff value for CDAI remission is <=2.8.

Simplified Disease Activity Index (SDAI) is the numerical sum of five outcome parameters: TJC and SJC (based on a 28-joint assessment), PtGA and PhGA (based on 0-10 cm VAS, where 0 = no disease activity and 10 = worst disease activity), and CRP. SDAI total score ranges from 0 (no disease activity) to 86 (maximal disease activity), where higher scores represents higher disease activity. The SDAI =< 3.3 indicates disease remission, > 3.4 to 11 indicates low disease activity, > 11 to 26 indicates moderate disease activity, and > 26 indicates high disease activity

The SDAI was the numerical sum of five outcome parameter: SJC and TJC (based on a 28-joint assessment), PGA and MDG (based on 0-10 cm VAS, where 0 = no disease activity and 10 = worst disease activity), and CRP. The SDAI =< 3.3 indicates disease remission

The 36-Item Short Form Health Survey (SF-36v2) is a questionnaire used to assess functional health and well-being and consists of eight domains: Physical Functioning, Role-Physical, Bodily Pain, General Health, Vitality, Social Functioning, Role-Emotional and Mental Health.

The SF-36v2 is summarized into Physical Component Summary (PCS) and Mental Component Summary (MCS) scores. The PCS and MCS scores range from 0 to 100, with 0=worst score (or quality of life) and 100=best score. A positive change from baseline indicates improvement.

The FACIT-Fatigue Scale consists of 13 items designed to measure the degree of fatigue experienced by the patient in the previous 7 days. For each question, there are five possible responses: 0 (not at all), 1 (a little bit), 2 (somewhat), 3 (quite a bit), 4 (very much).

A total fatigue score is calculated by summing all items, and possible total scores range from 0 (maximum fatigue) to 52 (no fatigue). A positive change from baseline indicates an improvement in the patient's fatigue (less fatigue).

Tender Joint Count: a total of 68 joints will be assessed for tenderness. Each joint is assessed for the presence/absence of tenderness. 68 joints are assessed for tenderness and joints are classified as tender/not tender giving a total possible tender joint count score of 0 to 68. A negative change from Baseline indicated improvement.

Swollen Joint Count: a total of 66 joints will be assessed for swelling. Each joint is assessed for the presence/absence of swelling. 66 joints were assessed for swelling and joints are classified as swollen/not swollen giving a total possible swollen joint count score of 0 to 66. A negative change from Baseline indicated improvement.

Patient's Assessment of Pain over the previous 24 hours: using a Visual Analog Scale (VAS) left end of the line 0=no pain to right end of the line 100=unbearable pain

Participant-assessed arthritis pain was scored on a 100-mm VAS, where the distance from 0 mm represented the participant's self evaluation of arthritis pain (0 mm=none; 100 mm=very severe). Change from baseline at a particular time point was calculated among patients with data available at both baseline and the time point of interest, where negative change indicated a decrease in participant-assessed arthritis pain.

Physician's assessment of participant's disease activity was scored on a 100-mm VAS, where the distance from 0 mm represented the physician's assessment of the participant's disease activity (0 mm=very good; 100 mm=very poor). Change from baseline at a particular time point was calculated among patients with data available at both baseline and the time point of interest, where negative change from baseline indicated an improvement in physician-assessed disease activity.

C-reactive protein is a biological marker of inflammation and is measured in nanograms per milliliter (ng/mL)

The Stanford Health Assessment Questionnaire disability index is a patient-reported outcome used to assess difficulty in performing activities of daily living. It consists of 20 questions referring to eight domains: dressing/grooming, arising, eating, walking, hygiene, reach, grip and common daily activities.

To respond to each question, a four-level response with higher scores showing larger functional limitations, was chosen. Scoring is as follows with respect to performance of participant's everyday activities: 0 (equals)=without difficulties; 1= with some difficulties; 2=with great difficulties; and 3=unable to perform these actions at all. The composite HAQ-DI score is the mean of the eight domain scores and the score ranges from 0 (no functional impairment) to 3 (maximum functional impairment). A negative change from baseline indicates improvement.

The Pharmacokinetics (PK) evaluation may include, but will not be limited to, plasma GDC-0853 concentrations and population PK model estimated PK exposures (area under the plasma concentration-time curve [AUC]. AUC was measured in Nanograms(ng) per millilitre(mL)*hour (hr)

Cmax is the maximum (peak) plasma concentration over the dosing interval at steady state (ss)

Cmin is the minimum concentration over the dosing interval at steady state (ss)

Participants of Cohort 1 received GDC-0853 mid dose, orally twice daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received GDC-0853 high dose, orally once daily along with placebo matched to adalimumab, subcutaneously every 2 weeks (Q2W) starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 milligrams per week (mg/week) (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 2 received GDC-0853 high dose, orally twice daily for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 2 received placebo matched to GDC-0853, orally twice daily for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

ITT population

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received GDC-0853 high dose, orally once daily along with placebo matched to adalimumab, subcutaneously every 2 weeks (Q2W) starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 milligrams per week (mg/week) (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 2 received GDC-0853 high dose, orally twice daily for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 2 received placebo matched to GDC-0853, orally twice daily for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received GDC-0853 mid dose, orally twice daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received GDC-0853 high dose, orally once daily along with placebo matched to adalimumab, subcutaneously every 2 weeks (Q2W) starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 milligrams per week (mg/week) (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 2 received placebo matched to GDC-0853, orally twice daily for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received GDC-0853 mid dose, orally twice daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received GDC-0853 high dose, orally once daily along with placebo matched to adalimumab, subcutaneously every 2 weeks (Q2W) starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 milligrams per week (mg/week) (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with placebo matched to adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 1 received placebo matched to GDC-0853, orally once daily along with adalimumab, subcutaneously Q2W starting on Day 1 for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 2 received GDC-0853 high dose, orally twice daily for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.

Participants of Cohort 2 received placebo matched to GDC-0853, orally twice daily for 12 weeks. Participants remained on a stable background therapy of MTX 15-25 mg/week (oral or parenteral; for participants entering the trial on MTX doses 15 mg/week, doses as low as 7.5 mg/week were allowed only if there was clear documentation in the medical record that higher doses were not tolerated or that the dose of MTX is the highest acceptable dose based on local clinical practice guidelines) and folic acid of at least 5 mg total dose weekly (or equivalent) as per investigators discretion.