APPLICABILITY OF IMMUNOGLOBULIN SEQUENCING TO ACCURATELY MONITOR DISEASE: AN ANALYSIS OF UNIQUENESS AMONG DIFFUSE LARGE B‐CELL LYMPHOMA PATIENTS TESTED BY CLONOSEQ

Abstract

Introduction: Diffuse Large B-Cell Lymphoma (DLBCL), an aggressive form of non-Hodgkin lymphoma, most commonly affects older adults. ∼80% of patients achieve complete response to frontline therapy; roughly half are cured while half relapse and receive salvage treatment such as transplant or CAR-T therapy which may be curative. Due to the aggressiveness of DLBCL and therapies offering potential cure, there is growing interest in a monitoring tool that provides more accurate information than standard clinical imaging. clonoSEQ® is a next-generation sequencing assay, which monitors measurable residual disease (MRD) levels from plasma of DLBCL patients. Using data from 1268 patients we assessed Ig loci uniqueness. Methods: Following identification of a dominant sequence(s) in a high tumor burden sample, the clonoSEQ algorithm quantifies tumor-associated sequences in MRD samples. The algorithm assigns a uniqueness score to each dominant sequence based on analyses of Ig locus V, D, and J segments and non-templated nucleotides. This score reflects the probability a sequence could be independently recreated in a non-malignant cell, including in another person, and is incorporated into the limit of detection (LOD). Sequences with a lower uniqueness must be observed at a higher rate to be above the LOD and reflect confidence they are tumor related. To assess the uniqueness of sequences detected across DLBCL patients, we examined our database containing 3657 dominant sequences from 1268 patients. 969 of these patients are from 27 clinical studies, and 302 are from use of the commercial assay. We assessed the dominant sequences for their uniqueness distribution across IgH, IgK, and IgL loci. Results: Across the population of 1268 DLBCL patients and 3657 dominant sequences, there was a range of 1–9 dominant sequences with 1115 (87.9%) patients having 1–4 (avg 2.89; med 3). We found that 1187 (93.6%) patients had at least one dominant IgH sequence. The remaining 81 (6.4%) patients had only dominant light chain sequences with 66 (5.2%) patients having IgK only. We assessed the distribution of uniqueness across the Ig loci in these patients. Figure 1a shows that IgH sequences were most unique, followed by IgL, IgH (D-J segments), and IgK. Figure 1b indicates the uniqueness score for each patient with only one dominant sequence, with just 31 (2.4%) subjects with expected ‘backgrounds’ of >1/100,000 of all Ig sequences. Keyword: diagnostic and prognostic biomarkers Conflicts of interests pertinent to the abstract A. Jacob Employment or leadership position: Adaptive Biotechnologies Stock ownership: yes, as an employee L. W. Lee Employment or leadership position: Adaptive Biotechnologies Stock ownership: yes, as an employee K. Akers Employment or leadership position: Adaptive Biotechnologies Stock ownership: yes, as an employee I. Kirsch Employment or leadership position: Adaptive Biotechnologies Stock ownership: yes, as an employee H. Simmons Employment or leadership position: Adaptive Biotechnoloigies Stock ownership: yes, as an employee