Inclusion Criteria:

          -  Male or female patients 18 years of age or older

          -  Histologic confirmation of non-muscle invasive bladder cancer of the transitional cell
             carcinoma high-grade subtype

          -  Histologically confirmed presence of CIS (with or without Ta or T1 disease) or
             histologically confirmed presence of high-grade Ta or T1 disease (without CIS)

          -  Absence of resectable disease after transurethral resection (TURBT) procedures
             (residual carcinoma in situ (CIS) acceptable; patients with T1 tumors must undergo
             repeat resection and biopsy [inclusive of muscularis propria] if initial biopsy did
             not include muscularis propria)

          -  BCG-unresponsive disease as defined as: (a) Persistent high-grade disease or
             recurrence within 6 months of receiving at least two courses of intravesical BCG (at
             least five of six induction doses and at least two of three maintenance doses); or (b)
             T1 high-grade disease at the first evaluation following induction BCG alone (at least
             5 of six induction doses)

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2

          -  Voluntary written informed consent and HIPAA authorization and agree to comply with
             all protocol-specified procedures and follow-up evaluations

        Exclusion Criteria:

          -  Recurrence > 6 months after last BCG instillation

          -  Life expectancy <2 years

          -  Any of the following clinical laboratory values at the time of enrollment: (1)
             Absolute neutrophil count (ANC) <800/µL or (2) Platelets < 50,000/µL

          -  Liver function abnormalities as indicated by ongoing hepatic enzyme elevation (AST or
             ALT) >2 times upper limit of normal (ULN)

          -  Renal insufficiency as indicated by a creatinine level >3 times ULN

          -  Evidence of muscle-invasive or regional and/or distant metastatic bladder cancer

          -  New York Heart Association (NYHA) Class III or IV heart failure or other clinical
             signs of severe cardiac dysfunction

          -  Symptomatic congestive heart failure (CHF), severe/unstable angina pectoris, or
             myocardial infarction within 6 months prior to study entry

          -  History or evidence of uncontrollable central nervous system (CNS) disease

          -  Active systemic infection requiring parenteral antibiotic therapy. All prior
             infections must have resolved following optimal therapy

          -  Concurrent febrile illness, active urinary tract infection, active tuberculosis, a
             history of hypotension or anaphylactic reactions

          -  Ongoing chronic systemic steroid therapy required (>10 mg oral prednisone daily or
             equivalent)

          -  Women who are pregnant or nursing. Female patients of childbearing potential must have
             a negative pregnancy test and must adhere to using a medically acceptable method of
             birth control prior to screening and agree to continue its use during the study and
             for 30 days after the last dose of study drug, or be surgically sterilized (e.g.,
             hysterectomy or tubal ligation). Women of childbearing potential are defined as any
             female who has experienced menarche and who is NOT permanently sterile or
             postmenopausal. Postmenopausal is defined as 12 consecutive months with no menses
             without an alternative medical cause. Males must agree to use barrier methods of birth
             control while on study and for 90 days post last dose of study drug.

          -  Patients currently receiving investigational or commercial anti-cancer agents or
             anti-cancer therapies other than BCG, ALT-803 and supportive care therapies.

          -  Concurrent use of other investigational agents

          -  Other illness or condition, including laboratory abnormalities, which in the opinion
             of the Investigator would exclude the patient from participating in this study. This
             includes, but is not limited to, serious medical conditions or psychiatric illness
             likely to interfere with participation in the study.