Participants in Part 2 (Pt. 2) receive MK-2206 (dosed either QOD or QW) taken orally at the maximum tolerated dose defined in Part 1 (Pt. 1 MTD). MK-2206 is administered in combination with trastuzumab (IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk) as well as lapatinib 500 mg taken orally once daily (QD).

Participants in Pt. 2 receive MK-2206 (dosed either QOD or QW) taken orally at the Pt. 1 MTD. MK-2206 is administered in combination with trastuzumab (IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk) as well as lapatinib 750 mg taken orally QD.

Participants in Part 2 (Pt. 2) receive MK-2206 (dosed either QOD or QW) taken orally at the Pt. 1 MTD. MK-2206 is administered in combination with trastuzumab (IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk) as well as lapatinib 1000 mg taken orally QD.

Trastuzumab will be administered as a 90-minute IV infusion at a loading dose of 8 mg/kg followed by 6 mg/kg q3wk.

Lapatinib tablets will be administered orally QD in doses of 500 mg, 750 mg, or 1000 mg.

The maximum tolerated dose (MTD) of MK-2206 in combination with trastuzumab (Part 1) was assessed for both QOD and QW dosing schedules. To calculate MTD, a dose-response curve for the rate of patients in each treatment combination arm experiencing a DLT in Cycle 1 will be estimated using the pooling-of-adjacent-violators algorithm, with this dose-response curve used to determine the MTD. The MTD is defined as the dose at which the percentage of patients experiencing a DLT is the closest to 25% or 30% in Part 1 and Part 2, respectively. As the study was terminated prior to Part 2 enrollment, the MTD of MK-2206 in combination with trastuzumab/lapatinib could not be determined.

The recommended phase 2 dose (RP2D) of MK-2206 in combination with trastuzumab (Part 1) was assessed. Data from Part 1 informing the determination of the MTD (i.e. DLTs in cycle 1), along with safety and tolerability data, and the pharmacokinetic profile was used to determine the RP2D for both the QOD and QW dosing of MK-2206 in combination with trastuzumab. As the study was terminated prior to Part 2 enrollment, the RP2D of MK-2206 in combination with trastuzumab/lapatinib could not be determined.

Participants in Pt. 1 receive MK-2206 135 mg QW, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.

Participants in Pt. 1 receive MK-2206 200 mg QW, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.

Total of all reporting groups

Participants in Pt. 1 receive MK-2206 60 mg QOD, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.

Participants in Pt. 1 receive MK-2206 135 mg QW, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.

Participants in Pt. 1 receive MK-2206 200 mg QW, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.

The number of participants discontinuing study drug due to an AE was assessed. An AE is defined as any unfavorable and unintended change in the structure, function, or chemistry of the body temporally associated with the use of the sponsor's product, whether or not considered related to the use of the product. Further, any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a preexisting condition which is temporally associated with the use of the sponsor's product, is also an AE.

All participants in Part 1 receiving ≥1 dose of study medication (i.e. all participants as treated). Due to trial termination, participants were not enrolled in Part 2; Part 2-specific arms are not included for analysis.

A DLT is a drug-related AE not related to disease progression or intercurrent illnesses. Toxicities are graded in severity according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCICTCAE) version 3.0. The following are considered DLTs: A.) Hematologic [grade 4 neutropenia (≥5 days); grade 3/4 neutropenia; grade 4 thrombocytopenia.] B.) Non-Hematologic [any grade ≥3 non-hematologic toxicity except: grade 3 nausea, vomiting, diarrhea, or dehydration; asthenia; hypersensitivity; grade 3 elevated transaminases (1 week).] C.) Additional [any drug-related AE leading to MK-2206 dose modification; grade ≥2 drug-related AE causing drug interruption (≥8 days); any drug-related AE causing drug interruption (≥15 days); grade ≥3 glucose intolerance with grade ≥2 hyperglycemia; fasting glucose >250 mg/dL (≥2 days); grade ≥3 electrolyte abnormality; lactoacidosis or ketoacidosis; non-fasting grade 4 hyperglycemia; increased QTc interval; significant bradycardia.].

All participants in Part 1 receiving ≥1 dose of study drug were included: 1) if experiencing a DLT in cycle 1; or 2) if not experiencing a DLT in cycle 1, received 90% of planned doses and completed all safety evaluations by ≤20 days after first dose of MK-2206. Trial terminated before Part 2 enrollment; Part 2-specific arms excluded.

The maximum tolerated dose (MTD) of MK-2206 in combination with trastuzumab (Part 1) was assessed for both QOD and QW dosing schedules. To calculate MTD, a dose-response curve for the rate of patients in each treatment combination arm experiencing a DLT in Cycle 1 will be estimated using the pooling-of-adjacent-violators algorithm, with this dose-response curve used to determine the MTD. The MTD is defined as the dose at which the percentage of patients experiencing a DLT is the closest to 25% or 30% in Part 1 and Part 2, respectively. As the study was terminated prior to Part 2 enrollment, the MTD of MK-2206 in combination with trastuzumab/lapatinib could not be determined.

All participants in Part 1 receiving ≥1 dose of study medication (i.e. all participants as treated), categorized by QOD or QW dosing of MK-2206. Due to trial termination, participants were not enrolled in Part 2; MTD could not be calculated for Part 2.

The recommended phase 2 dose (RP2D) of MK-2206 in combination with trastuzumab (Part 1) was assessed. Data from Part 1 informing the determination of the MTD (i.e. DLTs in cycle 1), along with safety and tolerability data, and the pharmacokinetic profile was used to determine the RP2D for both the QOD and QW dosing of MK-2206 in combination with trastuzumab. As the study was terminated prior to Part 2 enrollment, the RP2D of MK-2206 in combination with trastuzumab/lapatinib could not be determined.

All participants in Part 1 receiving ≥1 dose of study medication (i.e. all participants as treated), categorized by QOD or QW dosing of MK-2206. Due to trial termination, participants were not enrolled in Part 2; RP2D could not be calculated for Part 2.

Participants in Pt. 1 receive MK-2206 60 mg QOD, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.

Participants in Pt. 1 receive MK-2206 135 mg QW, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.

Participants in Pt. 1 receive MK-2206 200 mg QW, taken orally. In combination with MK-2206, trastuzumab is administered by IV infusion at an initial dose of 8 mg/kg (loading dose) followed by 6 mg/kg q3wk.