Printer-Friendly pageAACR 2007 IR Abstract
Author Block: K. Milner, K. Mason, T. Theriault, M. Mayo, K. Tate, D.W. Denney, Jr.
Genitope Corporation, Fremont, CA
Purpose: MyVax® personalized immunotherapy is being evaluated in a blinded Phase 3 study for previously untreated fNHL patients who achieve at least a partial response to a standard course of chemotherapy and maintain that response for 6-months. After randomization, 2/3 of patients received 7 immunizations with MyVax® personalized immunotherapy over 24 weeks, while 1/3 received a KLH-KLH conjugate control. MyVax® personalized immunotherapy consists of the patient- and tumor-specific Id protein, produced using molecular techniques, conjugated to KLH (Id-KLH) and administered in a series of subcutaneous injections with the adjuvant granulocyte-macrophage colony-stimulating factor (GM-CSF). Id is the collection of unique immunogenic epitopes on an immunoglobulin. KLH is a carrier protein used to increase antigen immunogenicity. Quantitative Enzyme Linked Immunosorbent Assays (ELISAs) have been developed to evaluate immune responses (IRs) to the Id and KLH components of the immunotherapy. Patients’ sera were evaluated for both anti-KLH and anti-Id IRs.
Method: Dilutions of pre- and post-immunization serum samples from each patient were added to a maleic anhydride microtiter plate coated with KLH or autologous Id. Bound antibody was detected with a biotinylated antihuman IgG1, 2, 4 antibody cocktail (BDB Pharmingen) followed by streptavidin conjugated horseradish peroxidase (Vector Labs). A human anti-KLH reference curve was utilized in order to attain quantitative data for the anti-KLH ELISA. Sera from 20 individuals who were previously immunized with MyVax® personalized immunotherapy were pooled to generate the anti-KLH reference standard. An anti-Id reference curve was utilized in order to attain quantitative data for the anti-Id ELISA. For this reference curve a chimeric mouse: human monoclonal antibody reactive against heavy chain variable region sub-family specific epitopes was developed.
Results: To date, blinded sera from 219 immunized patients have been evaluated. These quantitative ELISAs allowed clear distinction between positive and negative IR for both anti-Id and anti-KLH responses. All patients have mounted an IR to KLH and 63/219 (29%) patients have mounted an IR to Id. The median anti-KLH and anti-Id IR levels were calculated for all patients at each visit. The median anti-KLH and anti-Id IRs peak at 2 weeks after immunization 7 and decline over the course of the follow up period.
Conclusions: Humoral IRs to KLH and Id occur in patients receiving MyVax® personalized immunotherapy. Novel quantitative ELISA methods will enable rigorous analysis of IR kinetics over the course of immunization and across different treatment regimens. Evaluation of these methods as a clinical trial endpoint is underway.
AACR 2007 MRD Abstract
Author Block: I. Valisheva, N. Kautz, T. Theriault, K. Mason, R. Abramson, MyVax® Personalized Immunotherapy Phase 3 Investigator Group, M. Mayo, M. E. Rybak, and D. W. Denney, Jr. Genitope Corporation, Fremont, CA
MyVax®personalized immunotherapy, an active immunotherapy targeting the idiotype (Id) of surface immunoglobulin (Ig) on malignant B cells, is currently in a blinded pivotal Phase 3 study. Id is the collection of unique immunogenic epitopes on an Ig molecule. MyVax®personalized immunotherapy is being evaluated for patients who achieve at least a partial response after 8 cycles of cyclophosphamide, vincristine, prednisone (CVP) and maintain the response over a 6-month rest period. After randomization, 2/3 of patients then received 7 immunizations with MyVax® personalized immunotherapy over 24 weeks, while 1/3 received a control immunotherapy.
Monitoring MRD via circulating tumor cells in peripheral blood lymphocytes (PBLs) may provide important information regarding disease status and response to therapy in FL patients. A standard method of assessing MRD in FL is by PCR amplification of the t(14;18) translocation at the major breakpoint region (MBR) locus near the BCL-2 gene. This assay has limited utility since studies have shown that 30-50% of FL tumors are not detected, while non-tumor cells may be identified. MRD assays were performed on DNA samples isolated from patient PBLs collected before and 6 months after chemotherapy and following study immunizations.
Three TaqMan®qPCR assays were performed on each patient sample analyzed: 1) Id-specific, 2) MBR, and 3) albumin. An Id-specific qPCR assay that detects the unique Ig present on tumor cells was developed for each individual patient using tumor Ig-specific primers and TaqMan®probes that span the CDR2/CDR3 region of the Ig heavy chain. The MBR and albumin assays utilized a set of standardized reagents for all patients. The albumin assay was used to normalize the MBR and Id-specific assay. The Id-specific and MBR assays can quantify one tumor cell per 100,000 PBLs, with an average reaction efficiency ~ 95%. While remaining blinded to the treatment group assignment, the relationship between the Id-specific and BCL-2 assays was compared with clinical outcome for over thirty patients. We conclude that the Id-specific assay can be used to detect MRD in peripheral blood of FL patients, including those who are BCL-2 negative. The Id-specific assay can be designed during the production of MyVax® personalized immunotherapy and utilized throughout the course of treatment to monitor the status of the patient’s disease.