UAB 9405 
March 16, 1994 
PAGE -6 
the effects of repeated immunization with and without pre-treatment with cytoxan 
on CEA specific immune responses (also to be conducted by Drs. Conry and 
LoBuglio). 
2.5 Pre-clinical studies with a polynucleotide vaccine composed of the plasmid 
DNA construct for human CEA can induce immune response and protection 
against tumor challenge in a syngeneic murine adenocarcinoma model 
expressing human CEA. 
We have carried out pre-clinical studies in a murine model of syngeneic colon 
adenocarcinoma (40) which have shown that a polynucleotide vaccine composed 
of the c-DNA for CEA can induce humoral immunity and cellular immunity 
(lymphoblastic transformation and lymphokine release to CEA) to human CEA. 
We have subsequently tested individual doses ranging from 10 pg to 250 pg while 
the intramuscular injection of 50 pg three times per week for a total of 18 
injections produced no evidence of local toxicity or inflammation at the injection 
site or systemically. Mice immunized with any one of a number of doses and 
schedules had evidence of immune response approximately 4 to 6 weeks post- 
immunization with immunoprotection against tumor challenge with 2x10^ tumor 
cells given from 3 to 8 weeks post-start of vaccination. These immune responses 
and protection against tumor challenge were of similar magnitude as that seen 
with recombinant vaccinia-CEA studies described above. The intramuscular 
injection of a plasmid containing the cDNA for chloramphenicol acetyltransferase 
produced no CEA immune responses and did not protect against tumor challenge. 
2.6 Patients with CEA positive metastatic colorectal cancer patients represent 
reasonable candidates to test the feasibility of polynucleotide vaccination as a 
means to induce immune response to tumor relevant and control antigens. 
Patients with metastatic colorectal cancer who have failed to respond or relapsed 
after 5-FU therapy regimens have <10% clinically relevant response rates to 
second and third line therapy options. Such patients represent reasonable 
populations for early phase I trials of appropriate anti-tumor therapy protocols. 
We have utilized such patient groups in trials of monoclonal antibodies (44), I- 
labeled genetically engineered monoclonal antibodies (45) and drug conjugates of 
monoclonal antibodies (46, protocol ongoing). 
2.7 Polynucleotide vaccines should have a favorable safety profile, particularly 
as compared to other gene therapy strategies for cancer. 
A variety of strategies have been proposed to approach cancer utilizing the 
techniques of gene therapy (reviewed in 47). These include genetic strategies to 
correct the mutational lesions characterizing cancer cells (“mutation 
compensation”), genetic strategies to eradicate tumor cells by encoded toxin genes 
(“molecular chemotherapy”) and genetic strategies to enhance immune 
mechanisms of tumor rejection (“genetic immunopotentiation”). One of the 
advantages of the latter strategy is that it capitalizes on the ability of the immune 
Recombinant DNA Research, Volume 19 [403] 
