Development of a novel idiotype-specific quantitative PCR (qPCR) assay for detecting minimal residual disease (MRD) in the peripheral blood from patients with follicular lymphoma (FL): relationship to a BCL-2 qPCR assay and clinical outcome Free

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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, and 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 35-50% 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 1 tumor cell per 100,000 PBLs, with an average reaction efficiency of ~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 30 patients. We conclude that the Id-specific assay can be used to detect MRD in peripheral blood of FL patients, including those that 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.