Inclusion Criteria:

- Must have a histologically confirmed diagnosis of renal cell carcinoma (clear cell or
predominately clear cell component). Papillary histology may also be enrolled
(maximum of 6 patients)

- Must be diagnosed with relapsed or Stage IV disease that is medically or surgically
unresectable and that has progressed after systemic therapy, including at least one
agent in the general class of kinase inhibitors (TKI not required for papillary
histology)

- Must have measurable/evaluable metastatic disease sites that have not previously
received radiotherapy and which does not require palliative intervention (at the time
of enrollment). Patients with non-measurable/evaluable disease are ineligible

- Must have at least one tumor lesion that displays uptake of 99mTc-EC20

- Must be > than or = 18 years of age

- Women must either be 1)not of child-bearing potential of 2)have a negative serum
pregnancy test within 7 days prior to commencing treatment with investigational
agents

- Must have completed prior cytotoxic chemotherapy, radiotherapy, immunotherapy or
experimental therapy 30 or more days prior to study enrollment, and recovered (or
returned to baseline) from associated acute toxicities. This restriction excludes
palliative radiotherapy.

- Must have an ECOG score less than or equal to 2

- Must have adequate hematologic, renal, and heptic function

Exclusion Criteria:

- Must not have a history of severe hypersensitivity (grade 3 - 4 allergic reaction) to
fluorescein, radiological contrast agent, cytokines, or have received fluorescein
within 30 days of the study

- Must not have medical conditions that preclude the use of IL-2 or IFN-α.

- Must not be pregnant or breast-feeding

- Must not be currently undergoing chemotherapy, anticancer hormonal therapy, and/or
therapy with immunosuppressant agents

- Must not be currently receiving bisphosphonates such as Zometa® (unless started >
four weeks prior to treatment with EC90/GPI-0100, in which case they can be
continued)

- Must not have any concomitant malignancy with the exception of basal cell or squamous
cell carcinoma of skin

- Must not have radiographically documented evidence of current brain metastases, a
history of stem cell transplant, immunodeficiency, and/or a medical or psychiatric
illness (that in the investigator's opinion, would prevent adequate compliance with
study therapy or evaluation of the endpoints)

- Must not have been administered another radiopharmaceutical that would interfere with
the assessment of 99mTc-EC20

- Must not be unable to tolerate conditions for radionuclide imaging