Anti-idiotype vaccine in colorectal cancer patients

Vaccination of patients with advanced ovarian carcinoma with the anti-idiotype ACA125: immunological response and survival (phase Ib/II)

PURPOSE

A Phase I/IIb multicenter study was conducted to evaluate the safety and immunogenicity of the anti-idiotypic antibody vaccine ACA125 that functionally imitates the tumor antigen CA125 in 119 patients with advanced ovarian carcinoma. A preliminary report on the initial 42 patients demonstrated safety and immunogenicity.

EXPERIMENTAL DESIGN

Using the complete intention-to-treat population (n = 119) who received a mean of 9.7 ACA125 applications, survival was analyzed with respect to immunological responses.

RESULTS

In 81 patients (68.1%), a specific anti-anti-idiotypic antibody (Ab3) response could be induced. Additionally, the development of CA125-specific antibodies (Ab1') and antibody-dependent cell-mediated cytotoxicity of CA125-positive tumor cells was observed in 50.4% and 26.9% of patients, respectively. The median survival of all patients was 19.4 months (range, 0.5-56.1 months). Ab3-positive patients showed a significantly longer survival (median, 23.4 months; P < 0.0001) as compared with Ab3-negative patients (median, 4.9 months). A positive Ab3 response remained associated with longer survival when controlling for other prognostic factors including FIGO (International Federation of Gynecologists and Obstetricians) stage, response to and type of first-line chemotherapy, number of previous treatments, or concomitant antitumor therapy. With regard to safety, repeated vaccination was well tolerated. No serious adverse events related to the application of ACA125 occurred.

CONCLUSIONS

Although the uncontrolled design of this study prevents definitive conclusions with respect to subgroups, the data support a relationship between Ab3 response and survival time. Thus, the need for further randomized, controlled clinical trials to establish efficacy of the vaccine ACA125 seems to be indicated.

Strategies for mimicking Neisserial saccharide epitopes as vaccines

Monoclonal antibody (mAb) 2C7 recognizes a conserved and widely expressed oligosaccharide (OS) epitope on Neisseria gonorrhoeae. This OS epitope evokes a significant bactericidal and opsonic immune response after natural infection and vaccination. The OS epitope structure represents an excellent target for a potential protective gonococcal vaccine. Because carbohydrate antigens are T-cell independent, inducing weak antibody responses, OS molecules are not useful immunogens. We developed and examined two different strategies to mimic the 2C7 OS epitope: (i) an anti-idiotope (mAb CA1); and (ii) a peptide (PEP-1). These surrogate immunogens elicited antibody responses in mice (CA1 and PEP-1) and rabbits (CA1) that were bactericidal in vitro against gonococci. Both CA1 and PEP-1 are true immunologic mimics of OS and may form a basis for the development of vaccine candidates for human immunization against N. gonorrhoeae.

Cancer vaccines: a step towards prevention and treatment of cancer

Breakthroughs in basic science and applied biology over the last quarter of a century have had a great deal of influence on our understanding of disease processes. The structure, function and importance of various lipid and protein molecules within cells is now well known and is central in future developments of diagnostic and therapeutic modalities. Since the discovery of the double helix DNA structure by Watson and Crick, molecular biology has come a long way enabling inroads to be made in manipulating DNA and evolving into the discipline of molecular oncology. For tumours having a viral carcinogenesis, preventive vaccines directed against viruses reduce the chance of tumour formation. Therapeutic vaccination, on the other hand, is less successful. To overcome the latter, various methods involving the use of tumour-specific antibodies, anti-idiotypic antibodies, peptides, proteins and carbohydrate products of human tumours, etc. have been tried. However, as the majority of human tumours are antigenic and not immunogenic, the problem remains. Recently, inoculation with DNA plasmids, encoding a variety of proteins, has been able to generate T-cell specific responses in vivo. This novel concept may help scientist to overcome the immunological tolerance and anti-tumour ineffectiveness induced by many human cancer cells and may lead to generation of tumour-specific vaccines.

Milestones in the development of Lym-1 therapy

Lym-1, a monoclonal antibody (MAb) that preferentially targets malignant lymphocytes, has induced therapeutic remissions in patients with advanced non-Hodgkin's lymphoma (NHL) or chronic lymphocytic leukemia (CLL) when labeled with iodine-131 (131I). Based on the strategy of fractionating the total radiation dose, trials were designed to define the safety, toxicity, and efficacy of a series of doses of 131I-Lym-1 given 2-6 weeks apart. All patients had disease resistant to standard therapy. 131I-Lym-1 was given after unconjugated Lym-1 and the 131I dose was escalated in Phase I-II trials. Therapy proved safe. The dose-limiting toxicity was thrombocytopenia. Nonhematological toxicities did not exceed grade 2 except for infrequent instances of grade 3 hypotension. In a low-dose (LD) trial of 131I-Lym-1, tumor regression occurred in 25 (83%) of 30 patients and 17 (57 %) had durable remissions; 3 of the remissions were complete. In a maximum tolerated dose (MTD) trial of 131I-Lym-1, 10 (71%) of 14 entries that received at least two doses of 131I-Lym-1 therapy and 11 (52%) of 21 total entries had remissions; 7 of the remissions were complete. All 3 entries in the MTD cohort of 100 mCi/m2 [3.7 MBq/m2] of body surface area had durable complete remissions. Therapeutic remission and human anti-mouse antibody (HAMA) after Lym-1 therapy were associated with increased survival that was significant in multivariate analyses. Evidence for an Ab3 idiotypic network with an antibody cytotoxic for Raji human lymphoma was found in the only patient examined in detail thus far; this patient was studied because she had a high titer, HAMA and prolonged survival. In conclusion, 131I-Lym-1 induced durable remissions in patients with chemotherapy-resistant NHL or CLL and was associated with acceptable toxicity. In a subset of the patients, survival was quite prolonged perhaps related to development of Ab3.

Prolonged survival associated with immune response in a patient treated with Lym-1 mouse monoclonal antibody

A patient with aggressive, chemotherapy-resistant non-Hodgkins lymphoma (NHL) was treated with 131I-Lym-1, a mouse antibody, on a protocol designed for serial therapy. Human anti-mouse antibody (HAMA) developed within 1 month of initial therapy. The patient also developed an antibody to the hypervariable region of the Lym-1 antibody (Lym-1 specific). Because the patient was responding to therapy, plasmaphoresis was used to reduce the level of HAMA followed by unlabeled Lym-1 calculated to be sufficient to block residual HAMA. This allowed additional therapy on three subsequent occasions over 5 months. Despite very high HAMA levels, no untoward effects from administrations of Lym-1 were observed. The HAMA response of the patient included anti-Lym-1 specific antibodies containing anti-idiotypic antibodies. The anti-Lym-1 antibody level has been sustained over the 9 year interval since 131I-Lym-1 therapy and has been associated with a uniquely long remission of the patient's disease. These observations demonstrate that, under certain circumstances, radioimmunotherapy (RIT) can be given safely and effectively despite HAMA. Anti-idiotypic antibodies could have induced an immune cascade that contributed to the prolonged disease-free survival of the patient.

Future directions for the treatment of colorectal carcinoma

Most of these therapies, although still in the infant stages of their development, offer the potential for major advances in colorectal cancer therapy. Gene therapy is an entirely new medicinal paradigm for the treatment of cancer. Currently, the clinical application of these methods is limited by the need for a more through understanding of cancer immunology and the availability of better vector systems for efficient and selective tumor gene transfer. As increasing numbers of scientists and clinicians address these issues, better therapies will likely emerge.

Immunological responses to the tumor-associated antigen CA125 in patients with advanced ovarian cancer induced by the murine monoclonal anti-idiotype vaccine ACA125

We have generated an immunoglobulin G1 (IgG1) murine monoclonal anti-idiotype antibody (Ab2) designated ACA125, which mimics a specific epitope on the tumor-associated antigen CA125. This antigen is expressed by most of malignant ovarian tumors. Patients with CA125-positive tumors are immunologically tolerant to CA125. We used ACA125 as a surrogate for the tumor-associated antigen CA125 for vaccine therapy of 16 patients with advanced epithelial ovarian cancer or recurrences. Each of the patients received a minimum of 3 injections up to 19 injections of the complete anti-idiotype MAb ACA125 at a dosage of 2 mg per injection. Nine of 16 patients developed anti-anti-idiotypic (Ab3) responses to the ACA125. All 9 patients generated specific anti-CA125 antibody demonstrated by reactivity with purified CA125. Nine of 16 patients developed a CA125-specific cellular immune response by their peripheral blood lymphocytes (PBL) and 3 of 16 showed an increase in gamma-interferon concentrations accompanied by Ab3 responses. Toxicity was limited to abdominal pain in one case, which led to the withdrawal of further immunizations. The median progression free survival in those patients, who showed a specific immune response to the tumor-associated antigen CA125, was 11.0 +/- 5.6 months without any other therapy, in contrast to 8.0 +/- 4.2 months in the anti-anti-idiotype negative group. This is the first report of the induction of a specific active immunity to the tumor-associated antigen CA125 in patients with advanced ovarian cancer treated with an anti-idiotype antibody that "mimics" CA125. Patients showed the development of a specific humoral and cellular immune response to an otherwise nonimmunogenic tumor antigen. The immune responses in patients treated with this anti-idiotype vaccine, the low rate of side effects, and the improved time to progression after the induction of a specific immune response against the tumor-associated antigen CA125 justify follow-up clinical trials in advanced ovarian cancer patients with minimal residual disease in an adjuvant approach.

A monoclonal antiidiotypic antibody ACA 125 mimicking the tumor-associated antigen CA 125 for immunotherapy of ovarian cancer

A new concept of oncological immunotherapy comprises the attempt to trigger the immune system of the host into a response against tumor cells. Antiidiotypic antibodies bearing the internal image of an antigen expressed on the surface of the tumor seem to be most suited for this purpose. We have generated a murine antiidiotypic antibody (ACA 125) functionally imitating the tumor-associated antigen CA 125, which can be detected in about 80% of ovarian carcinomas. The hybridoma cell was adapted to serum-free medium and antibody was produced in a hollow fiber cell culture system (Technomouse). ACA 125 (Ab2) shows high affinity for the paratope of Ab1 (affinity constant: 2.3 x 10(9) liters/mol) and binding of Ab2 to Ab1 is completely inhibited by the nominal antigen. Application of F(ab')2 fragments of ACA 125 to rats lead to an anti-CA 125 immunity by production of IgG and IgM antiantiidiotypic antibodies (Ab3) that bind to both ACA 125 and CA 125. Furthermore the induction of a non-MHC-restricted cell-mediated cytotoxicity for human ovarian adenocarcinoma cell line NIH-OVCAR3 (expressing CA 125 on its surface) could be proved; additionally complement-dependent cytotoxicity (CDC) as well as an antibody-dependent cellular cytotoxicity (ADCC) was observed. Thus, monoclonal antiidiotypic antibody ACA 125 fulfills recent criteria for an antibody, which might be successful in immunotherapy using the anti-idiotypic network approach.