The purpose of this study is to learn whether it is safe and effective to administer HKI-272 (neratinib) in combination with paclitaxel in patients with breast cancer.

Inclusion Criteria:

Inclusion criteria for both parts of clinical trial:

• Good performance status
• Normal ejection fraction
• Adequate cardiac, kidney, and liver function
• Adequate blood counts
• At least one measurable target lesion
• Negative pregnancy test for female subjects

Inclusion Criteria for Part 1 Only:

- Pathologically confirmed solid tumor not curable with available standard therapy

Inclusion Criteria for Part 2 Only:

• Pathologically confirmed breast cancer
• HER2 positive tumor
• Prior treatment with Herceptin

Exclusion Criteria:

Exclusion criteria for both parts of clinical trial:

• Major surgery, radiotherapy, chemotherapy or investigational agents within two weeks of treatment day 1
• Subjects with bone or skin as the only site of disease
• Active central nervous system metastases
• Significant cardiac disease or dysfunction
• Significant gastrointestinal disorder
• Inability or unwillingness to swallow HKI-272 capsules
• Prior exposure to HKI-272 or other HER2 targeted agents, except trastuzumab (Part 2 only). Prior lapatinib is permitted in arm B of part 2.
• Treatment with a taxane within 3 months of treatment day 1
• Grade 2 or greater motor or sensory neuropathy
• Pregnant or breast feeding women
• Known hypersensitivity to paclitaxel or Cremophor EL
• Prior treatment with anthracyclines with cumulative dose of >400 mg/m^2
• Any other cancer within 5 years with the exception of contralateral breast cancer, adequately treated cervical carcinoma in situ, or adequately treated basal or squamous cell carcinoma of the skin

Exclusion Criteria for Part 2 Only:

- More than 1 (arm A) or 3 (arm B) prior cytotoxic chemotherapy regimen for metastatic disease