Inclusion Criteria:

- Histologically confirmed breast cancer meeting the following criteria:

- HER2-negative by any of the following:

- IHC 0-1+ without fluorescence in situ hybridization (FISH)

- IHC2+ with negative FISH

- HER2/CEP17 < 2.0 if only FISH is done

- Hormone receptor-negative

- Estrogen receptor-negative (ER-) and progesterone receptor-negative (PR-)
by IHC present in < 10% of invasive cancer cells

- Clinical stage II or III disease

- Measurable disease

- Clinically or radiologically measurable primary breast cancer tumor ≥ 2.0 cm

- No inflammatory breast cancer

- No history of invasive breast cancer treated with systemic chemotherapy

- History of ductal carcinoma in situ or lobular carcinoma in situ allowed

- Menopausal status unknown

- ECOG performance status (PS) 0-1 (Karnofsky 90-100%)

- WBC ≥ 3,000/mm³

- ANC ≥ 1,500/mm³

- Platelet count ≥ 100,000/mm³

- Hemoglobin ≥ 9 g/dL

- Total bilirubin normal

- AST and ALT < 2.5 times upper limit of normal (ULN)

- Creatinine < 1.5 times ULN OR creatinine clearance ≥ 60 mL/min

- Fertile patients must use two forms of contraception (i.e., barrier contraception
and one other method of contraception) ≥ 4 weeks prior to, during, and for ≥ 12
months after study treatment

- Negative pregnancy test

- Not pregnant or nursing

- Ability to swallow pills

- At least 5 years since other malignancy except for curatively treated carcinoma in
situ of the cervix, carcinoma in situ of the colon, melanoma in situ, and basal or
squamous cell carcinoma of the skin

- No history of allergic reactions attributed to compounds of similar chemical or
biological composition to gamma secretase inhibitor RO4929097 or other agents used in
the study

- No malabsorption syndrome or other condition that would interfere with intestinal
absorption

- Not serologically positive for hepatitis A, B, or C

- No history of liver disease, other forms of hepatitis, or cirrhosis

- No uncontrolled electrolyte abnormalities including hypocalcemia, hypomagnesemia, and
hypokalemia

- No symptomatic congestive heart failure, unstable angina pectoris, and a history of
torsades de pointes or other significant cardiac arrhythmias

- No uncontrolled intercurrent illness including, but not limited to, any of the
following:

- Ongoing or active infection

- Psychiatric illness and/or social situations that would limit compliance with
study requirements

- No baseline QTc > 450 msec in males or QTc > 470 in females

- No peripheral neuropathy ≥ grade 2

- No requirement for antiarrhythmics or other medications known to prolong QTc

- No prior radiotherapy, chemotherapy, or biotherapy for currently diagnosed breast
cancer

- Recovered to < NCI CTCAE grade 2 toxicities related to prior therapy

- No other concurrent investigational agents

- No concurrent medications with narrow therapeutic indices that are metabolized by
cytochrome P450 (CYP450), including warfarin sodium (Coumadin®)

- No concurrent medications that are strong inducers and/or inhibitors or substrates of
CYP3A4 or CYP2C8

- Switching to alternative medications allowed

- No concurrent combination antiretroviral therapy for HIV-positive patients