Immune Response and Potential Booster for Patients Who Have Received HER2-pulsed DC1

Inclusion Criteria:

- Patients with a diagnosis of nonmetastatic classic HER2pos (ie, IHC 3+ or FISHpos)
breast cancer (BC) who have previously been vaccinated with DC1 HER2-pulsed vaccines
on any of several prior clinical trials for ductal carcinoma in situ (DCIS) or
inflammatory breast cancer (IBC) are eligible; however, we also allowed HER2 2+
patients in many of these prior trials and they will also be allowed to participate in
this trial. Note: HER2pos BC is defined by tumor tissue HER2 overexpression and or
tumor HER2 amplification. The lack of HER2 overexpression by IHC is defined as 0 or 1+
whereas overexpression is defined as 3+. In the event of equivocal IHC, 2+, the tumor
must be gene-amplified by fluorescent in situ hybridization (FISH) performed upon the
primary tumor or metastatic lesion (ratio > 2 and HER2 copy number > 4 define
HER2negdisease).

- Participants must have completed all standard-of-care treatment for nonmetastatic BC
(e.g., surgery, chemotherapy, radiation therapy, and HER2-targeted therapy). Note:
antiestrogen therapy is permitted while on trial.

- Age ≥ 18 years.

- Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.

- Participants must have normal organ and marrow function within 2 weeks of
registration.

- Left ventricular ejection fraction above institutional lower limit of normal (by
echocardiogram or multigated acquisition (MUGA) scan within 6 months of registration).

- For both male and female patients, effective methods of contraception must be used
throughout the study and for 3 months following the last dose.

- Must have the ability to understand and the willingness to sign a written informed
consent prior to registration on study.

Exclusion Criteria:

- Uncontrolled intercurrent illness including, but not limited to, ongoing or active
infection, congenital prolonged QT syndrome, symptomatic congestive heart failure,
unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations
that would limit compliance with study requirements.

- Current use of immunosuppressive agents or systemic corticosteroids. Topical, ocular,
intra-articular, intranasal, inhalational corticosteroids (with minimal systemic
absorption) are allowed. Patients who have received systemic corticosteroids ≤ 30 days
prior to starting study drug will be excluded.

- No other prior malignancy is allowed except for the following:

- Adequately treated basal cell or squamous cell skin cancer

- In situ cervical cancer

- Any other cancer from which the patient has been disease free for at least 3
years.

- Pregnant or breast feeding.

- Known to be HIV positive.

- Known current or a history of hepatitis B or C virus, including chronic and dormant
states, unless disease has been treated and confirmed cleared.

- Major surgery within 4 weeks of initiation of study drug.

- Have not recovered to ≤ Grade 1 or tolerable Grade 2 adverse events (AEs) due to
agents administered ≥ 28 days earlier, as documented by the treating investigator.

- Currently enrolled in any other clinical protocol or investigational trial that
involves administration of experimental therapy and/or therapeutic devices, or
investigational drug.

- Not able to comply with the treatment schedule and study procedures for any reason.

- Have stage IV BC.