A Study of Trastuzumab Emtansine, Paclitaxel, and Pertuzumab in Patients With HER2-Positive, Locally Advanced or Metastatic Breast Cancer

An AE is defined as any untoward medical occurrence in a participant or clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered to be related to the medicinal product. An SAE is any untoward medical occurrence that, at any dose, results in death, is life threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, or results in a congenital anomaly/birth defect.

DLT is defined as one of the following toxicities related to study drug during Cycle 1, according to the NCI CTCAE, Version 3: Grade 3 or higher non-hematologic AEs; Grade 3 or higher elevation of serum bilirubin, hepatic transaminases, or alkaline phosphatase; Grade 4 or higher thrombocytopenia; Grade 4 or higher neutropenia; any subjectively intolerable toxicity related to T-DM1, paclitaxel, or pertuzumab; any treatment-related toxicity prohibiting the start of the second cycle of treatment and/or prompting to a dose delay or modification during the DLT observation period, such as prompting a dose reduction at Cycle 2 Day1.

The MTD was defined as the highest dose of T-DM1 and paclitaxel at which 0 of 3 participants or 1 of 6 experienced a DLT, when T-DM1 (Q3W or QW) and paclitaxel (QW) was administered with and without pertuzumab treatment.

The MTD was defined as the highest dose of paclitaxel at which 0 of 3 participants or 1 of 6 experienced a DLT, when paclitaxel (QW) and T-DM1 (Q3W or QW) was administered with and without pertuzumab treatment.

Participants in Phase IIa received T-DM1 Q3W and paclitaxel in Group A and T-DM1, paclitaxel, and pertuzumab in Group B.

Participants were assessed for toxicity prior to each dose of T-DM1 and paclitaxel; dosing occurred only if the clinical assessment and laboratory test values were acceptable. Dose modifications included dose delayed or any dose reduction. Participants in whom significant toxicities had not recovered to the treatment range defined by the dose modification guidelines at the time of their next scheduled dose, had their dose of T-DM1 and/or paclitaxel delayed or reduced for up to 21 days.

Cmax of serum T-DM1 and total trastuzumab (sum of conjugated and unconjugated trastuzumab) in Cycle 1 was estimated by non-compartmental analysis for Phase Ib when T-DM1 was administered Q3W.

Cmax of plasma DM1 in Cycle 1 was estimated by non-compartmental analysis for Phase Ib when T-DM1 was administered Q3W.

AUC0-21 for serum T-DM1 and total trastuzumab (sum of conjugated and unconjugated trastuzumab) in Cycle 1 was estimated by non-compartmental analysis for Phase Ib when T-DM1 was administered Q3W.

Cmax for serum T-DM1 and total trastuzumab (sum of conjugated and unconjugated trastuzumab) in Cycle 1 was estimated by non-compartmental analysis when T-DM1 was administered QW.

Cmax for plasma DM1 in Cycle 1 was estimated by non-compartmental analysis for Phase Ib when T-DM1 was administered QW

AUClast for serum T-DM1 and serum total trastuzumab (sum of conjugated and unconjugated trastuzumab) in Cycle 1 was estimated by non-compartmental analysis for Phase Ib when T-DM1 was administered QW

Plasma Cmax of paclitaxel (65 mg/m^2 and 80 mg/m^2) for Cycle 1 (in the absence T-DM1) and Cycle 2 (in the presence T-DM1) was estimated by non-compartmental analysis.

Plasma AUC0-inf of paclitaxel (65 mg/m^2 and 80 mg/m^2) was estimated by non-compartmental analysis in Cycle 1 (in the absence T-DM1) and Cycle 2 (in the presence T-DM1).

Plasma t1/2 of paclitaxel (65 mg/m^2 and 80 mg/m^2) was estimated by non-compartmental analysis in Cycle 1 (in the absence T-DM1) and Cycle 2 (in the presence T-DM1).

Plasma CL of paclitaxel (65 mg/m^2 and 80 mg/m^2) was estimated by non-compartmental analysis for in Cycle 1 (in the absence T-DM1) and Cycle 2 (in the presence T-DM1).

Volume of distribution is defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired blood concentration of a drug. Vss is the apparent volume of distribution at steady-state which is estimated by (D/AUC[0-inf]) X (AUMC[0-inf])/AUC[0-inf]) where D is the dose of study drug, AUMC(0-inf) is the area under the first moment curve extrapolated to infinity and AUC(0-inf) is the area under the plasma concentration-time curve from time zero to infinite time. The Vss of paclitaxel (65 mg/m2 and 80 mg/m2) is observed in Cycle 1 (in the absence of T-DM1) and Cycle 2 (in the presence of T-DM1).

Change in cardiac functions i.e., left ventricular ejection fraction (LVEF) and segmental wall abnormalities were assessed by echocardiogram or multigated acquisition scans. LVEF was assessed as change from baseline as 0 to <15%, >=15 to <25%, >=25%, and missing values.

Participants with measurable disease (at least one lesion 2 centimeters [cm] or more on computed tomography (CT) scan or 1 cm or more on spiral CT scan) were considered for OR. ORR is defined as the percentage of patients with a complete response (CR)/partial response (PR) determined on two consecutive tumor assessments at least 4 weeks apart based on modified Response Evaluation Criteria in Solid Tumors, Version 1.0 (RECIST). CR defined as disappearance of all target and non-target lesions and normalization of tumor marker level. PR defined as at least 30 percent decrease in sum of the longest diameters of the target lesions taking as reference the baseline sum longest diameters.

Duration of OR is only calculated for participants with OR and is defined as the time from the first tumor assessment that supports the participant's OR to disease progression or death.

Clinical benefit is defined as CR, PR, or stable disease (SD) of 6 months or more duration as assessed by the investigator. CR and PR are identified in previous outcome measure. SD is defined as neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for progressive disease (PD), taking as reference the smallest sum longest diameter since the treatment started. PD is defined as at least a 20% increase in the sum of the longest diameter of target lesions, taking as reference the smallest sum longest diameter recorded since the treatment started or the appearance of one or more new lesions.

PFS is defined as the time from the first day of study treatment to documented disease progression or death on study i.e., death due to any cause within 30-days of last dose of study treatment, whichever occurs first.