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Tucatinib

Phase 3

Anatomic Stage II Breast Cancer AJCC v8 | Small molecule | Oncology |Pfizer, Inc.|Last Updated: Jul 22, 2026

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Trial Design
RandomizedDouble-BlindACTIVE_CONTROLLEDDMCBiomarker
Total Trials1
Total Enrollment1,056
FDA Designations
No designations recorded
Clinical trial landscape

Tucatinib · 21 trials · 36 indications

Phase 3 4Phase 2 9Phase 1 8
NCT05253651A Study of Tucatinib With Trastuzumab and mFOLFOX6 Versus Standard of Care Treatment in First-line HER2+ Metastatic Colorectal CancerColorectal Neoplasms
RECRUITING400 Analytics
NCT05132582A Study of Tucatinib or Placebo With Trastuzumab and Pertuzumab for Metastatic HER2+ Breast CancerHER2 Positive Breast Cancer
ACTIVE NOT_RECRUITING654 Analytics
NCT04457596T-DM1 and Tucatinib Compared With T-DM1 Alone in Preventing Relapses in People With High Risk HER2-Positive Breast Cancer, the CompassHER2 RD TrialAnatomic Stage II Breast Cancer AJCC v8
ACTIVE NOT_RECRUITING1,056 Analytics
NCT03975647A Study of Tucatinib vs. Placebo in Combination With Ado-trastuzumab Emtansine (T-DM1) for Patients With Advanced or Metastatic HER2+ Breast CancerHER2-positive Breast Cancer
ACTIVE NOT_RECRUITING466 Analytics
PHASE3RECRUITING
A Study of Tucatinib With Trastuzumab and mFOLFOX6 Versus Standard of Care Treatment in First-line HER2+ Metastatic Colorectal Cancer
Colorectal NeoplasmsUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
A Study of Tucatinib or Placebo With Trastuzumab and Pertuzumab for Metastatic HER2+ Breast Cancer
HER2 Positive Breast CancerUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
T-DM1 and Tucatinib Compared With T-DM1 Alone in Preventing Relapses in People With High Risk HER2-Positive Breast Cancer, the CompassHER2 RD Trial
Anatomic Stage II Breast Cancer AJCC v8Unlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
A Study of Tucatinib vs. Placebo in Combination With Ado-trastuzumab Emtansine (T-DM1) for Patients With Advanced or Metastatic HER2+ Breast Cancer
HER2-positive Breast CancerUnlock trial analytics
Study Endpoints
Primary Endpoints
Progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST v1.1) by Blinded Independent Central Review (BICR)
Up to approximately 3 years

The time from the date of randomization to the BICR assessment of disease progression according to RECIST v1.1 or death from any cause

Progression-free survival (PFS) by investigator assessment per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1
Up to approximately 3 years

The time from the date of randomization to the investigator assessment of disease progression according to RECIST v1.1 or death from any cause

Modified invasive disease-free survival (iDFS)
From randomization to one of the following events: invasive local, regional or distant recurrence, invasive contralateral breast cancer or death from any cause, assessed up to 10 years

A Kaplan-Meier method will be used to estimate the survival curves and a stratified log-rank test will be used to compare the invasive disease-free survival (iDFS) of the two arms. A stratified Cox model will be used to estimate the hazard ratio. If there appears to be clinically significant imbalances of baseline variables between the treatment arms, a secondary analysis of the primary endpoint will use stratified Cox model to compare the treatment effects that include the variables that are deemed imbalanced between the arms as adjusting variables. The randomization stratification variables will be the stratified variables in the model.

Progression-Free Survival (PFS) as Per Response Evaluation Criteria in Solid Tumors (RECIST) Version (v)1.1 Based on Investigator Assessment
From the date of randomization to the date of PD or death from any cause or censoring date, whichever occurred first (maximum up to 43 months)

PFS as per investigator was defined as the time from the date of randomization to the investigator assessment of disease progression (PD) as per RECIST v1.1 or death from any cause, whichever occurred first. PD: at least a 20 percent (%) increase in the sum of diameters of target lesions, taking as reference the smallest sum on study. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of at least 5 millimiter (mm). Participants without documentation of PD, or death at the time of analysis were censored at the date of the last tumor assessment.

Objective response rate (ORR) to assess the anti-tumor activity of tucatinib in combination with Doxil using RECIST v1.1.
Up to approximately 40 months.

Proportion of participants with confirmed complete response (CR) or partial response (PR) to tucatinib in combination with Doxil according to RECIST v1.1 criteria.

Incidence of Adverse Events, Graded According to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) Version (v) 5.0
through study completion; an average of 1 year.
Confirmed Objective Response Rate(cORR) Per Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1 Determined by Independent Central Review (ICR): Japanese Participants
From date of first dose until first documented disease progression or start of new anticancer therapy, whichever occurred first (maximum up to 17.8 months)

cORR was defined as percentage of participants with confirmed complete response (CR) or partial response (PR), per RECIST version 1.1. CR: disappearance of all target lesions. Any pathological lymph nodes must have a reduction in short axis to \<10 millimeter(mm). PR: a \>=30% decrease in the sum of diameters of target lesions, taking as a reference the baseline sum diameters. Only response assessments before first documented progressive disease(PD) or new anti-cancer therapies were considered. PD: at least a 20% increase in sum of diameters of target lesions, taking as reference the smallest sum on study(included baseline sum if smallest on study). In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of at least 5 mm. Appearance of one or more new lesions was also considered PD. Participants with missing data were considered non-responders. cORR was determined by ICR. Two-sided 90% exact confidence interval was based on Clopper-Pearson method.

Number of Participants With Dose-limiting Toxicities (DLT) During the First Cycle of Treatment
Cycle 1 (28 days)

DLTs were adverse events (AEs), laboratory abnormalities, or treatment modifications that occurred during the first cycle of treatment in the Phase 2 paclitaxel dose optimization stage that were related to paclitaxel, to tucatinib, or to the combination of tucatinib, trastuzumab, ramucirumab and paclitaxel and that met any of the study protocol specified criteria. The relationship of AEs to study drugs was determined by the investigator. AEs that were attributed only to trastuzumab and/or ramucirumab, but not tucatinib or paclitaxel were not considered DLTs.

Number of Participants With Treatment-emergent Adverse Events (TEAEs)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment (maximum treatment duration= 19.8 months, maximum follow-up duration up to 20.8 months)

An AE was any untoward medical occurrence in a participant or clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. AEs were defined as treatment emergent if they were newly occurring or worsened following study treatment. A TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, ramucirumab, or paclitaxel) and up to 30 days after the last dose of study treatment (tucatinib, trastuzumab, ramucirumab, or paclitaxel, whichever was later).

Number of Participants With Treatment-emergent Laboratory Abnormalities
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment (maximum treatment duration= 19.8 months, maximum follow-up duration up to 20.8 months)

Treatment-emergent laboratory abnormalities were defined as abnormalities that are new or worsened on or after receiving the first dose of study treatment up to 30 days after the last dose of study treatment. Laboratory abnormalities included: 1) Blood chemistry: alanine aminotransferase increased, albumin decreased, alkaline phosphatase increased, aspartate aminotransferase increased, calcium corrected for albumin decreased, calcium corrected for albumin increased, creatinine increased, glomerular filtration rate estimated decreased, glucose decreased, lactate dehydrogenase increased, magnesium decreased, magnesium increased, potassium decreased, potassium increased, sodium decreased, sodium increased, and total bilirubin increased; 2) Hematological: hemoglobin decreased, leukocytes decreased, lymphocytes decreased, neutrophils decreased, and platelets decreased.

Number of Participants With Clinically Significant Vital Signs Values
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment (maximum treatment duration= 19.8 months, maximum follow-up duration up to 20.8 months)

Vital sign examinations included systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate. Criteria: SBP greater than or equal to (\>=) 120 millimeters of mercury (mm Hg) or DBP \>= 80 mm Hg; SBP \>= 140 mm Hg or DBP \>= 90 mm Hg; SBP \>= 160 mm Hg or DBP \>= 100 mm Hg), heart rate greater than (\>) 100 beats per minute (min). Clinical significance in vital signs abnormalities was judged by investigator. In this outcome measure number of participants with at least 1 clinically significant abnormality in any vital sign are reported.

Maximum Percentage Change From Baseline in Weight
From Baseline (Day 1) up to 30 days after the last dose of study treatment (maximum treatment duration= 19.8 months, maximum follow-up duration up to 20.8 months)

Maximum percentage decrease from baseline in weight is reported in this outcome measure.

Number of Participants With Any Dose Modifications
From first dose of the study treatment (Day 1) up to the last dose of study treatment (maximum treatment duration up to 19.8 months)

Dose modification included dose hold, dose reduction, dose error and unplanned dose adjustments. Number of participants with any dose treatment modifications for paclitaxel, ramucirumab, trastuzumab, and tucatinib are reported in this outcome measure.

Confirmed Objective Response Rate (cORR) as Assessed by Investigator
From the first dose of study treatment until the first documented CR or PR on or before the first documented PD or new anti-cancer therapies or death, whichever occurred first (up to 28.3 months)

Confirmed ORR was defined as the percentage of participants with best overall response of complete response (CR) or partial response (PR) according to Response Evaluation Criteria in Solid Tumors (RECIST) criteria version (v)1.1 as assessed by investigator and was considered as confirmed when subsequent response was at least 4 weeks after initial response. As per RECIST v1.1, CR: disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to less than (\<)10 millimeter (mm). PR: at least a greater than or equal to (\>=)30 % decrease in the sum of diameters (SOD) of target lesions (longest for non-nodal target lesions and the short axes for nodal target lesions), taking as reference the baseline sum diameters. Disease progression (PD): at least \>=20% relative increase in SOD of target lesion taking as reference the smallest sum on study (including baseline sum if that is the smallest on study).

Confirmed Objective Response Rate (cORR) Per Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1 According to Investigator (INV) Assessment
From the first dose of study treatment until the first documented PD or before start of any new anti-cancer therapy (up to 43 months)

Confirmed objective response rate was defined as the percentage of participants with a confirmed complete response (CR) or partial response (PR) per investigator according to RECIST v1.1. For a response to be considered confirmed, the subsequent response had to be at least 4 weeks after the initial response. CR: disappearance of all target lesions and non-target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to less than (\<)10 millimeters (mm). PR: a greater than equal to (\>=) 30 percent (%) decrease in the sum of diameters of target lesions, taking as reference the baseline sum of diameters. 95% exact confidence interval (CI) was based on Clopper-Pearson method.

Number of Participants With Renal Dose-Limiting Toxicities (DLTs): Phase 1b (Cohort 1A and 1B)
From first dose of tucatinib until end of Cycle 3 (up to 42 days)

A renal DLT was defined as an increase in serum cystatin C \>1.5\* baseline that was not related to pre-renal or post-renal etiologies (including disease progression, dehydration and intercurrent illness) and occurred during the period of treatment with tucatinib in combination with trastuzumab and FOLFOX between the first dose of tucatinib and the end of Cycle 3. Increased serum cystatin C for which there was an alternative clinical explanation (eg, clearly related to an intercurrent illness or disease progression) was not considered renal DLTs.

Number of Participants With Treatment Emergent Adverse Events (TEAEs): Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

An adverse event (AE) was defined as any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil, oxaliplatin and pembrolizumab) through 30 days after the last dose of study treatment.

Number of Participants With Treatment Related TEAEs: Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil, oxaliplatin and pembrolizumab) through 30 days after the last dose of study treatment. Treatment related TEAEs were AEs related to any study treatment and relatedness was judged by investigator.

Number of Participants With Greater Than or Equal to (>=) Grade 3 TEAEs: Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil, oxaliplatin and pembrolizumab) through 30 days after the last dose of study treatment. TEAEs were graded according to National Cancer Institute, Common Terminology Criteria for Adverse Events (NCI-CTCAE) version (v) 5.0 where grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening. Number of participants with \>= grade 3 TEAEs are reported in this outcome measure.

Number of Participants With >= Grade 3 Treatment Related TEAEs: Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil, oxaliplatin and pembrolizumab) through 30 days after the last dose of study treatment. TEAEs were graded according to NCI-CTCAE v 5.0 where grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening. Treatment related TEAEs were AEs related to study treatment and relatedness was judged by investigator. Number of participants with \>= grade 3 treatment related TEAEs are reported in this outcome measure.

Number of Participants With Any Serious Adverse Event (SAE): Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

An SAE was any untoward medical occurrence at any dose that was fatal; life-threatening; required hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect or was medically significant.

Number of Participants With Any Treatment Related SAE: Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

An SAE was any untoward medical occurrence at any dose that was fatal; life-threatening; required hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect or was medically significant. Treatment related SAEs were SAEs related to any study treatment and relatedness was judged by investigator.

Number of Participants With DLTs: Phase 1b (Cohort 1E)
Cycle 1 (Up to 21 days)

DLTs were AEs/ laboratory abnormalities that were considered to be related to tucatinib/ tucatinib in combination with chemotherapy(mFOLFOX6/CAPOX) and/or trastuzumab and/or pembrolizumab. DLTs was defined any of following: a-)Hepatic- any instance of aspartate aminotransferase(AST)/ alanine aminotransferase(ALT)\>3\*upper limit of normal(ULN) and total bilirubin \>2\*ULN that is not thought to be due to progressive disease(PD)/other medical illness. PD:at least 20% increase in sum of diameters of target lesions,taking as reference smallest sum on study. In addition to relative increase of 20%,sum must also demonstrate an absolute increase of at least 5 millimeters(mm). b-) Non-hematologic- any clinically significant, non-hematologic treatment-related AE\>= grade(G)3, with following exceptions:G3 fatigue=\< 7days,G3 diarrhea,nausea/vomiting without optimal use of anti-emetics/antidiarrheals c-)hematologic:\>=G3 febrile neutropenia and absolute neutrophil count(ANC) decreased G4 for \>7days.

Number of Participants With DLTs: Phase 1b (Cohort 1F)
Cycle 1 (Up to 28 days)

DLTs were AEs/ laboratory abnormalities that were considered to be related to tucatinib/ tucatinib in combination with chemotherapy (mFOLFOX6/CAPOX) and/ or trastuzumab and/ or pembrolizumab. DLTs was defined any of following: a-) Hepatic- any instance of AST/ ALT \>3\*ULN and total bilirubin \>2\*ULN that is not thought to be due to PD/ other medical illness. PD: at least 20% increase in sum of diameters of target lesions, taking as reference smallest sum on study. In addition to relative increase of 20%, sum must also demonstrate an absolute increase of at least 5 mm. b-) Non-hematologic- any clinically significant, non-hematologic treatment-related AE\>= grade 3, with following exceptions: grade 3 fatigue=\< 7days, grade 3 diarrhea, nausea/vomiting without optimal use of anti-emetics/antidiarrheals c-) hematologic: \>= grade 3 febrile neutropenia and ANC decreased grade 4 for \>7days.

Number of Participants With Treatment Emergent Hematological Laboratory Abnormalities: Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

The following hematological parameters were assessed: hemoglobin decreased, leukocytes decreased, lymphocytes decreased, neutrophils decreased and platelets decreased. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil, oxaliplatin and pembrolizumab) through 30 days after the last dose of study treatment. Hematological laboratory abnormalities were graded according to NCI CTCAE v 5.0 (grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening). Participants with hematological abnormalities of any grade were reported.

Number of Participants With Treatment Emergent Chemistry Laboratory Abnormalities: Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

The following chemistry laboratory parameters were assessed: alanine aminotransferase (ALT) increased, albumin decreased, alkaline phosphatase increased, aspartate aminotransferase (AST) increased, calcium corrected for albumin decreased, creatinine increased, calcium corrected for albumin increased, lactate dehydrogenase increased, potassium decreased, potassium increased, sodium decreased, sodium increased and total bilirubin increased. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil, oxaliplatin and pembrolizumab) through 30 days after the last dose of study treatment Chemistry laboratory abnormalities were graded according to NCI CTCAE v 5.0 (grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening). Participants with chemistry abnormalities of any grade were reported.

Number of Participants With Clinically Significant Post-Baseline Vital Signs: Phase 1b (Cohort 1E and 1F)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.7 months)

Vital signs included temperature, blood pressure, heart rate and respiratory rate. Clinically significant vital signs were defined as: temperature greater than or equal to (\>=) 38 degrees Celsius, respiratory rate greater than (\>) 20 breaths per minute, systolic blood pressure (SBP) \>= 120 millimeter of mercury (mmHg) or diastolic blood pressure (DBP) \>= 80 mmHg, SBP \>= 140 mmHg or DBP \>= 90 mmHg and heart rate \> 100 beats per minute (bpm).

Number of Participants With TEAEs: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An AE was defined as any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment.

Number of Participants With Treatment Related TEAEs: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Treatment related TEAEs were AEs related to study treatment and relatedness was judged by investigator.

Number of Participants With >= Grade 3 TEAEs: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. TEAEs were graded according to NCI-CTCAE v 5.0 where grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening. Number of participants with \>= grade 3 TEAEs are reported in this outcome measure.

Number of Participants With >= Grade 3 Treatment Related TEAEs: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. TEAEs were graded according to NCI-CTCAE v 5.0 where grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening. Treatment related TEAEs were AEs related to study treatment and relatedness was judged by investigator. Number of participants with \>= grade 3 treatment related TEAEs are reported in this outcome measure.

Number of Participants With Any SAE: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An SAE was any untoward medical occurrence at any dose that was fatal; life-threatening; required hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect or was medically significant.

Number of Participants With Any Treatment Related SAE: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An SAE was any untoward medical occurrence at any dose that was fatal; life-threatening; required hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect or was medically significant. Treatment related SAEs were SAEs related to any study treatment and relatedness was judged by investigator.

Number of Participants With DLTs: Phase 1b (Cohort 1D)
Cycle 1 (Up to 28 days)

DLTs were AEs/ laboratory abnormalities that were considered to be related to tucatinib/ tucatinib in combination with chemotherapy (mFOLFOX6/CAPOX) and/ or trastuzumab and/ or pembrolizumab. DLTs was defined any of following: a-) Hepatic- any instance of AST/ ALT \>3\*ULN and total bilirubin \>2\*ULN that is not thought to be due to PD/ other medical illness. PD: at least 20% increase in sum of diameters of target lesions, taking as reference smallest sum on study. In addition to relative increase of 20%, sum must also demonstrate an absolute increase of at least 5 mm. b-) Non-hematologic- any clinically significant, non-hematologic treatment-related AE\>= grade 3, with following exceptions: grade 3 fatigue=\< 7days, grade 3 diarrhea, nausea/vomiting without optimal use of anti-emetics/antidiarrheals c-) hematologic: \>= grade 3 febrile neutropenia and ANC decreased grade 4 for \>7days.

Number of Participants With Treatment Emergent Hematological Laboratory Abnormalities: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

The following hematological parameters were assessed: hemoglobin decreased, leukocytes decreased, lymphocytes decreased, neutrophils decreased and platelets decreased. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Hematological laboratory abnormalities were graded according to NCI CTCAE v 5.0 (grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening). Participants with hematological abnormalities of any grade were reported.

Number of Participants With Treatment Emergent Chemistry Laboratory Abnormalities: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

The following chemistry parameters were assessed: ALT increased, albumin decreased, alkaline phosphatase increased, AST increased, calcium corrected for albumin decreased, creatinine increased, lactate dehydrogenase increased, potassium decreased, potassium increased, sodium decreased and sodium increased. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Chemistry laboratory parameters abnormalities were graded according to NCI CTCAE v 5.0 (grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening). Participants with chemistry abnormalities of any grade were reported.

Number of Participants With Clinically Significant Post-Baseline Vital Signs: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

Vital signs included temperature, blood pressure, heart rate and respiratory rate. Clinically significant vital signs were defined as: temperature \>= 38 degrees Celsius, respiratory rate \> 20 breaths per minute, SBP \>= 120 mmHg or DBP \>= 80 mmHg, SBP \>= 140 mmHg or DBP \>= 90 mmHg and heart rate \> 100 beats per minute (bpm).

Number of Participants With TEAEs Leading to Dose Holds: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An AE was defined as any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Dose hold was considered as dose delay and dose elimination. Number of participants with TEAEs leading to dose holds are reported in this outcome measure.

Number of Participants With TEAEs Leading to Dose Reductions: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An AE was defined as any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Number of participants with TEAEs leading to dose reductions are reported in this outcome measure.

Number of Participants With TEAEs Leading to Dose Discontinuations: Phase 1b (Cohort 1D)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 21 months)

An AE was defined as any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Number of participants with TEAEs leading to dose discontinuations (i.e. permanent withdrawal of tucatinib, trastuzumab, oxaliplatin, fluorouracil and leucovorin) are reported in this outcome measure.

Number of Participants With TEAEs: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment.

Number of Participants With Treatment Related TEAEs: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Treatment related TEAEs were AEs related to study treatment and relatedness was judged by investigator.

Number of Participants With >= Grade 3 TEAEs: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. TEAEs were graded according to NCI-CTCAE v 5.0 (grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening). Number of participants with \>= grade 3 TEAEs are reported in this outcome measure.

Number of Participants With >= Grade 3 Treatment Related TEAEs: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

An AE was defined was any untoward medical occurrence in a clinical investigational participant administered a medicinal product and which did not necessarily have a causal relationship with this treatment. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. TEAEs were graded according to NCI-CTCAE v 5.0 (grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening). Treatment related TEAEs were AEs related to study treatment and relatedness was judged by investigator. Number of participants with \>= grade 3 treatment related TEAEs are reported in this outcome measure.

Number of Participants With Any SAE: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

An SAE was any untoward medical occurrence at any dose that was fatal; life-threatening; required hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect or was medically significant.

Number of Participants With Any Treatment Related SAE: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

An SAE was any untoward medical occurrence at any dose that was fatal; life-threatening; required hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect or was medically significant. Treatment related SAEs were SAEs related to any study treatment and relatedness was judged by investigator.

Number of Participants With Treatment Emergent Hematological Laboratory Abnormalities: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

Following hematological parameters were assessed: hemoglobin decreased, leukocytes decreased, lymphocytes decreased, neutrophils decreased and platelets decreased. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Hematological abnormalities were graded according to NCI CTCAE v 5.0; where, grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening). Participants with hematologic abnormalities of any grade were reported.

Number of Participants With Treatment Emergent Chemistry Laboratory Abnormalities: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

Following chemistry parameters were assessed: ALT increased, albumin decreased, alkaline phosphatase increased, AST increased, creatinine increased, glomerular filtration rate (GFR) estimated decreased, lactate dehydrogenase increased, potassium decreased, potassium increased, sodium decreased, sodium increased and total bilirubin increased. TEAE was defined as a newly occurring or worsening AE after the first dose of study treatment (tucatinib, trastuzumab, leucovorin, fluorouracil and oxaliplatin) through 30 days after the last dose of study treatment. Chemistry abnormalities were graded according to NCI CTCAE v 5.0; where, grade 1= mild, grade 2= moderate, grade 3= severe and grade 4= life-threatening. Participants with chemistry abnormalities of any grade were reported.

Number of Participants With Clinically Significant Post-Baseline Vital Signs: Phase 2 (Cohort 2B)
From first dose of the study treatment (Day 1) up to 30 days after the last dose of study treatment, end of study date, death date, or data cutoff date, whichever was earlier (maximum of 20.9 months)

Vital signs included temperature, blood pressure and heart rate. Clinically significant vital signs were defined as: temperature \>= 38 degrees Celsius, respiratory rate \> 20 breaths per minute, SBP \>= 120 mmHg or DBP \>= 80 mmHg, SBP \>= 140 mmHg or DBP \>= 90 mmHg and heart rate \> 100 bpm.

Confirmed Objective Response Rate (cORR) Per RECIST v1.1 Per Blinded Independent Central Review (BICR) in Pooled Cohorts A+B
Up to 46.6 months

cORR was defined as the percentage of participants with confirmed CR or PR according to RECIST v1.1. CR was defined as the disappearance of all target lesions and each target lymph node must have reduction in short axis to less than (\<)1.0 centimeter (cm). PR was defined as at least a 30 percentage (%) decrease in post-baseline sum of the diameters (sum of the longest diameter for all target lesions plus the sum of the short axis of all the target lymph nodes at current evaluation) taking as reference the baseline sum of diameters.

Progression-free Survival (PFS) Per RECIST 1.1 as Determined by Blinded Independent Central Review (BICR)
34.6 months

Defined as the time from the date of randomization to the date of documented disease progression.

Percentage of participants with ≥1 adverse event (AE)
Up to approximately 2.5 years

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Percentage of participants discontinuing from study therapy due to AE
Up to approximately 2.5 years

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Maximum observed concentration (Cmax) of tucatinib
14 days
Cmax of ONT-993
14 days
Time of the maximum observed concentration (tmax) of tucatinib
14 days
Tmax of ONT-993
14 days
AUC from time 0 to the time of last quantifiable concentration (AUClast) of tucatinib
14 days
AUClast of ONT-993
14 days
AUC from time 0 to 12 hours postdose (AUC0-12hr) of tucatinib
14 days
AUC0-12hr of ONT-993
14 days
AUC from time 0 extrapolated to infinity (AUC0-inf) of tucatinib
1 day
AUC from time 0 extrapolated to infinity (AUC0-inf) of ONT-993
1 day
Percentage of AUC0-inf due to extrapolation (%AUCextrap) of tucatinib
1 day
%AUCextrap of ONT-993
1 day
Apparent total clearance (CL/F) of tucatinib
14 days
Apparent volume of distribution during the terminal phase (Vz/F) of tucatinib
14 days
Metabolite-to-parent molar ratio based on AUC (MRAUC) of ONT-993
14 days
Maximum observed plasma concentration (Cmax) of metformin
Up to 9 days
Time to maximum observed plasma concentration (tmax) of metformin
Up to 9 days
Half-life (t1/2) of metformin
Up to 9 days
Area under the plasma concentration-time curve from time 0 to the last available measurement (AUC0-last) of metformin
Up to 9 days
Area under the plasma concentration time curve to time 0 extrapolated to infinity (AUC0-inf) of metformin
Up to 9 days
Apparent volume of distribution (V2/F) of metformin
Up to 9 days
Oral clearance (CL/F) of metformin
Up to 9 days
Placebo-corrected change-from-baseline in QTcF
Up to 32 days

QTcF is the QT interval corrected for heart rate using Fridericia's method.

Maximum observed concentration (Cmax)
Up to 48 hours

Pharmacokinetic (PK) endpoint of tucatinib

Time of maximum observed concentration (Tmax)
Up to 48 hours

PK endpoint of tucatinib

Area under the concentration-time curve (AUC) from time 0 to the last quantifiable concentration (AUC[0-t])
Up to 48 hours

PK endpoint of tucatinib

AUC from time 0 to infinity (AUC[0-inf])
Up to 48 hours

PK endpoint of tucatinib

Percentage extrapolation for AUC (%AUCextrap)
48 hours

PK endpoint of tucatinib

Apparent terminal elimination rate constant (λz)
Up to 48 hours

PK endpoint of tucatinib

Apparent terminal elimination half-life (t½)
Up to 48 hours

PK endpoint of tucatinib

Apparent total clearance
Up to 48 hours

PK endpoint of tucatinib

Apparent volume of distribution during the terminal phase
Up to 48 hours

PK endpoint of tucatinib

Mean residence time (MRT)
Up to 48 hours

PK endpoint of tucatinib

Area under the concentration-time curve (AUC) from time 0 to infinity
Up to 22 days

PK parameters for tucatinib (Parts A, B, and C); repaglinide and its M4 metabolite (Part D), tolbutamide and its 4-hydroxytolbutamide metabolite (Part D), midazolam and its 1-hydroxymidazolam metabolite (Part D), and digoxin (Part E)

AUC from time 0 to the time of the last quantifiable concentration
Up to 22 days

PK parameters for tucatinib (Parts A, B, and C); repaglinide and its M4 metabolite (Part D), tolbutamide and its 4-hydroxytolbutamide metabolite (Part D), midazolam and its 1-hydroxymidazolam metabolite (Part D), and digoxin (Part E)

Percentage extrapolation in AUC
Up to 22 days

PK parameters for tucatinib (Parts A, B, and C); repaglinide and its M4 metabolite (Part D), tolbutamide and its 4-hydroxytolbutamide metabolite (Part D), midazolam and its 1-hydroxymidazolam metabolite (Part D), and digoxin (Part E)

Maximum observed concentration
Up to 22 days

PK parameters for tucatinib (Parts A, B, and C); repaglinide and its M4 metabolite (Part D), tolbutamide and its 4-hydroxytolbutamide metabolite (Part D), midazolam and its 1-hydroxymidazolam metabolite (Part D), and digoxin (Part E)

Time of maximum observed concentration
Up to 22 days

PK parameters for tucatinib (Parts A, B, and C); repaglinide and its M4 metabolite (Part D), tolbutamide and its 4-hydroxytolbutamide metabolite (Part D), midazolam and its 1-hydroxymidazolam metabolite (Part D), and digoxin (Part E)

Apparent terminal elimination half-life
Up to 22 days

PK parameters for tucatinib (Parts A, B, and C); repaglinide and its M4 metabolite (Part D), tolbutamide and its 4-hydroxytolbutamide metabolite (Part D), midazolam and its 1-hydroxymidazolam metabolite (Part D), and digoxin (Part E)

Apparent volume of distribution
Up to 22 days

PK parameters for tucatinib (Parts A, B, and C); repaglinide (Part D), tolbutamide (Part D), midazolam (Part D), and digoxin (Part E).

Metabolite-to-parent ratio based on AUC
Up to 22 days

PK parameters for M4 metabolite, 4-hydroxytolbutamide metabolite, and 1-hydroxymidazolam metabolite (Part D only)

Incidence of adverse events
12 months
Severity of adverse events
Up to approximately 4 years
Secondary Endpoints
Overall survival (OS)
Up to approximately 6 years
Confirmed objective response rate (cORR) per RECIST v1.1 by BICR
Up to approximately 3 years
PFS per RECIST v1.1 by investigator assessment
Up to approximately 3 years
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Study Design & Arms
AllocationRANDOMIZED
MaskingNONE
ModelPARALLEL
PurposeTREATMENT
Treatment Arms
ArmTypeDescription
Tucatinib ArmEXPERIMENTALTucatinib + trastuzumab + mFOLFOX6
Standard of Care ArmACTIVE_COMPARATOREither (1) mFOLFOX6, (2) mFOLFOX6 and bevacizumab, or (3) mFOLFOX6 and cetuximab
Tucatinib + trastuzumab + pertuzumabEXPERIMENTALTucatinib + trastuzumab + pertuzumab
Placebo + trastuzumab + pertuzumabACTIVE_COMPARATORPlacebo + trastuzumab + pertuzumab
Arm I (trastuzumab emtansine, placebo)ACTIVE_COMPARATORPatients receive T-DM1 IV over 30-90 minutes on day 1 and placebo PO BID on days 1-21. Treatment repeats every 21 days for up to 14 cycles in the absence of disease progression or unacceptable toxicity. Patients undergo echocardiography/multigated acquisition (MUGA) scan and blood sample collection throughout the study. Patients undergo echocardiography/multigated acquisition (MUGA) scan and blood sample collection throughout the study.
Arm II (trastuzumab emtansine, tucatinib)EXPERIMENTALPatients receive T-DM1 IV over 30-90 minutes on day 1 and tucatinib PO BID on days 1-21. Treatment repeats every 21 days for up to 14 cycles in the absence of disease progression or unacceptable toxicity. Patients undergo echocardiography/multigated acquisition (MUGA) scan and blood sample collection throughout the study.
Tucatinib + T-DM1EXPERIMENTALTucatinib + T-DM1
Placebo + T-DM1ACTIVE_COMPARATORPlacebo + T-DM1
Tucatinib Experimental Treatment ArmEXPERIMENTALParticipants will receive tucatinib 300mg by mouth twice daily continuously in combination with Doxil 40mg/m2 given intravenously on day 1 of each cycle. Cycles will be 28 days. Up to 36 participants will be enrolled in this Phase 2 study.
Tucatinib and Adotrastuzumab Emtansine (T-DM1)EXPERIMENTALEach study cycle is 21 days (3 weeks) Participants will take tablets of tucatinib two (2) times a day, about 8-12 hours apart. Participants will receive T-DM1 by vein over about 30 minutes on Day 1 of each cycle
Tucatinib + Trastuzumab + CapecitabineEXPERIMENTALParticipants will receive tucatinib plus trastuzumab plus capecitabine. Tucatinib 300 mg will be administered orally twice daily (BID). Trastuzumab 8 mg/kg loading dose followed by 6 mg/kg maintenance dose thereafter, will be administered intravenously (IV) on Day 1 of each 21-day cycle. Capecitabine 1000 mg/m\^2 will be administered orally BID on Days 1-14 of each 21-day cycle. Tucatinib, trastuzumab and capecitabine treatment will continue until unacceptable toxicity, disease progression, death, withdrawal of consent or study closure.
Phase 2 ArmEXPERIMENTALTucatinib + trastuzumab + ramucirumab + paclitaxel
Arm 3AEXPERIMENTALTucatinib + trastuzumab + ramucirumab + paclitaxel
Arm 3BACTIVE_COMPARATORRamucirumab + paclitaxel + tucatinib placebo + trastuzumab placebo
Arm 3CEXPERIMENTALTucatinib + ramucirumab + paclitaxel + trastuzumab placebo
Tucatinib + Trastuzumab (+ Fulvestrant)EXPERIMENTALTucatinib + trastuzumab (+ fulvestrant in hormone-receptor positive HER2-mutant breast cancer only)
Single ArmEXPERIMENTALTucatinib + trastuzumab deruxtecan
Cohort 1AEXPERIMENTALTucatinib + trastuzumab + FOLFOX given in 14-day cycles
Cohort 1BEXPERIMENTALTucatinib + trastuzumab + FOLFOX given in 14-day cycles
Cohort 1CEXPERIMENTALTucatinib + trastuzumab + CAPOX given in 21-day cycles
Cohort 1DEXPERIMENTALTucatinib + trastuzumab + FOLFOX. Tucatinib and FOLFOX given in 14-day cycles and trastuzumab given every 21 days
Cohort 1EEXPERIMENTALTucatinib + trastuzumab + pembrolizumab + FOLFOX. Tucatinib and FOLFOX given in 14-day cycles, trastuzumab given in 21-day cycles, and pembrolizumab given in 42-day cycles
Cohort 1FEXPERIMENTALTucatinib + trastuzumab + pembrolizumab + CAPOX. Tucatinib, trastuzumab, and CAPOX given in 21-day cycles and pembrolizumab given in 42-day cycles.
Cohort 1GEXPERIMENTALTucatinib + trastuzumab + pembrolizumab. Tucatinib and trastuzumab given in 21-day cycles and pembrolizumab given in 42-day cycles.
Cohort 2AEXPERIMENTALTucatinib + trastuzumab + pembrolizumab + (FOLFOX or CAPOX). Either (1) tucatinib and FOLFOX given in 14-day cycles or (2) tucatinib and CAPOX given in 21-day cycles. Trastuzumab given in 21-day cycles and pembrolizumab given in 42-day cycles.
Cohort 2BEXPERIMENTALTucatinib + trastuzumab + FOLFOX given in 14-day cycles.
Cohort A: Tucatinib + TrastuzumabEXPERIMENTALNon-randomized cohort. Participants take tucatinib twice per day orally on Days 1-21 and trastuzumab intravenously (into the vein; IV) on Day 1. Cycles repeat every 21 days.
Cohort B: Tucatinib + TrastuzumabEXPERIMENTALRandomized cohort. Participants take tucatinib twice per day orally on Days 1-21 and trastuzumab intravenously (into the vein; IV) on Day 1. Cycles repeat every 21 days.
Cohort C: Tucatinib MonotherapyEXPERIMENTALRandomized cohort. Participants take tucatinib twice per orally every day. Participants who do not respond to therapy may have the option to receive tucatinib and trastuzumab.
Tucatinib in combination with capecitabine & trastuzumabEXPERIMENTALTucatinib + capecitabine + trastuzumab
Placebo in combination with capecitabine & trastuzumabACTIVE_COMPARATORPlacebo + capecitabine + trastuzumab
Tucatinib TreatmentEXPERIMENTALChinese participants with HER2+ advanced breast cancer, gastric or gastroesophageal junction adenocarcinoma, or colorectal cancer receive tucatinib 300 mg by mouth twice daily during 21-day cycles. Treatment continues until there is evidence of unacceptable toxicity or documented progression.
Cohort 1EXPERIMENTAL50 mg twice daily on Days 1-13 and once daily on Day 14
Cohort 2EXPERIMENTAL150 mg twice daily on Days 1-13 and once daily on Day 14
Cohort 3EXPERIMENTAL300 mg twice daily on Days 1-13 and once daily on Day 14
Tucatinib plus metforminEXPERIMENTALTucatinib administered twice daily on Days 2-8. Metformin administered as a single dose on Days 1 and 8. Iohexol administered via IV push on Days 1 and 8
Treatment Sequence ABCEXPERIMENTALtucatinib + placebo + moxifloxacin (administered in sequential treatment periods)
Treatment Sequence CABEXPERIMENTALmoxifloxacin + tucatinib + placebo (administered in sequential treatment periods)
Treatment Sequence BCAEXPERIMENTALplacebo + moxifloxacin + tucatinib (administered in sequential treatment periods)
Treatment Sequence CBAEXPERIMENTALmoxifloxacin + placebo + tucatinib (administered in sequential treatment periods)
Treatment Sequence ACBEXPERIMENTALtucatinib + moxifloxacin + placebo (administered in sequential treatment periods)
Treatment Sequence BACEXPERIMENTALplacebo + tucatinib + moxifloxacin (administered in sequential treatment periods)
Group 1: HealthyACTIVE_COMPARATORMatch-controlled healthy subjects with normal hepatic function
Group 2: Mild Hepatic ImpairmentEXPERIMENTALSubjects with Mild hepatic impairment (Child-Pugh Class A, score of 5 or 6)
Group 3: Moderate Hepatic ImpairmentEXPERIMENTALSubjects with Moderate hepatic impairment (Child-Pugh Class B, score of 7 to 9)
Group 4: Severe Hepatic ImpairmentEXPERIMENTALSubjects with Severe hepatic impairment (Child-Pugh Class C, score of 10 to 14)
Part AEXPERIMENTALTucatinib plus Itraconazole
Part BEXPERIMENTALTucatinib plus Rifampin
Part CEXPERIMENTALTucatinib plus Gemfibrozil
Part DEXPERIMENTALTucatinib plus Repaglinide plus Tolbutamide plus Midazolam
Part EEXPERIMENTALTucatinib plus Digoxin
Tucatinib (ONT-380) in combination with T-DM1EXPERIMENTAL -
Tucatinib (ONT-380) in combination with capecitabineEXPERIMENTAL -
Tucatinib (ONT-380) in combination with trastuzumabEXPERIMENTAL -
Tucatinib (ONT-380) combined with capecitabine and trastuzumabEXPERIMENTAL -
Interventions
NameTypeDescription
tucatinibDRUG300mg given by mouth (orally) twice daily
trastuzumabDRUG8mg/kg loading dose will be given into the vein (IV; intravenously) on Cycle 1 day 1, followed by 6mg/kg given by IV every 3 weeks thereafter.
bevacizumabDRUG5mg/kg given by IV every 2 weeks
cetuximabDRUG400mg/m2 loading dose will be given by IV on Cycle 1 day 1, followed by 250mg/m2 given by IV weekly
oxaliplatinDRUG85mg/m2 given by IV every 2 weeks. Component of mFOLFOX6.
leucovorinDRUG400mg/ m2 given by IV every 2 weeks. Component of mFOLFOX6.
levoleucovorinDRUG200mg/ m2 given by IV every 2 weeks. May be given in place of leucovorin. Component of mFOLFOX6.
fluorouracilDRUG400mg/m2 given by IV bolus then 2400mg/m2 given by continuous IV infusion (over 46-48 hours) every 2 weeks. Component of mFOLFOX6.
PertuzumabDRUG420mg given by IV every 21 days
Combination product: Trastuzumab + PertuzumabDRUG600 mg pertuzumab, 600 mg trastuzumab, and 20,000 units hyaluronidase will be given by subcutaneous injection every 21 days. May be given in place of trastuzumab and pertuzumab individually.
PlaceboDRUGGiven orally twice daily
Trastuzumab EmtansineBIOLOGICALGiven IV
Placebo AdministrationDRUGGiven PO
Questionnaire AdministrationOTHERAncillary studies
Quality-of-Life AssessmentOTHERAncillary studies
T-DM1DRUG3.6 mg/kg given into the vein (IV; intravenously) every 21 days
DoxilDRUGParticipants will receive Doxil 40mg/m2 intravenously on day 1 of each 28 day cycle (with a maximum cumulative dose of 550mg/m2).
CapecitabineDRUGCapecitabine 1000 mg/m\^2 administered BID via oral tablet
ramucirumabDRUG8 mg/kg will be administered IV on Days 1 and 15 of each cycle
paclitaxelDRUG60 or 80 mg/m\^2 IV on Days 1, 8, and 15 of each cycle
tucatinib placeboOTHERGiven twice daily orally
trastuzumab placeboOTHERIV on Days 1 and 15 of each cycle
fulvestrantDRUGGiven into the muscle (intramuscular; IM) once every 4 weeks starting from Cycle 1 Day 1, plus one dose on Cycle 1 Day 15. Only administered to participants with hormone-receptor positive breast cancer.
trastuzumab deruxtecanDRUG5.4 mg/kg via intravenous (into the vein; IV) infusion on Day 1 of each of 21-day cycle
pembrolizumabDRUG400 mg given by IV on day 1 of cycle 1, then every 6 weeks.
MetforminDRUG850mg administered orally
IohexolDRUG1500 mg administered intravenously (IV)
moxifloxacinDRUG400mg single oral dose
itraconazoleDRUG200mg dose
rifampinDRUG600mg dose
gemfibrozilDRUG600mg tablets
repaglinideDRUG1mg dose
tolbutamideDRUG500mg dose
midazolamDRUG2mg dose
digoxinDRUG0.5 mg dose
Tucatinib (ONT-380)DRUGGiven twice per day, orally
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Eligibility Criteria
Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites366

Inclusion Criteria: * Histologically and/or cytologically confirmed adenocarcinoma of the colon or rectum which is locally advanced unresectable or metastatic * Able to provide the most recently available formalin-fixed paraffin-embedded (FFPE) tumor tissue blocks (or freshly sectioned slides) obta...

Countries:United StatesArgentinaAustraliaAustriaBelgiumBrazilCanadaChileChinaFranceGermanyGreeceIrelandItalyJapanNetherlandsNorwayPolandPortugalSlovakiaSouth KoreaSpainSwitzerlandTaiwanUnited KingdomCzechiaFinlandPuerto RicoDenmarkIsraelSingaporeSweden
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Recent Changes (Last 90 Days)
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