Immunotherapy: enlisting the immune system to fight cancer

In this trial, the researchers gave patients an intravenous dose of MFECP1, a recombinant fusion protein consisting of a fragment of an antibody raised against the substance carcinoembryonic antigen (CEA), which is produced by the cancer, and carboxypeptidase

G2 (CPG2), an enzyme that activates a prodrug. Then, researchers gave patients an intravenous bis-iodo phenol mustard prodrug which is activated by the enzyme within the cancer.

Anti-enzyme antibody developed in 40 percent of patients having a single treatment, 75 percent of patients after two treatments and 100 percent of patients after three treatments.

In addition, imaging scans showed that four of nine patients had partial response, meaning their tumors shrank, at a total prodrug dosage of at least 900 mg/m2. This response was confirmed by a 25 percent reduction in blood levels of CA 19-9, a tumor marker, in three patients who had raised levels before treatment. Stable disease, as defined by RECIST criteria, was seen in 69 percent of patients who had a total prodrug dose of at least 900 mg/m2.

The most common side effects were thrombocytopenia (low platelet count) and neutropenia (low white blood cell count). Side effects were deemed tolerable.

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