Larkin, James

Abstract Background Monoclonal antibody therapies (t-mabs) are known to interfere in serum immunofixation, as they show up as a discrete band. Until recently, most of the t-mabs were IgG kappa monoclonal immunoglobulins, and laboratories were familiar with the clue of a cathodal migrating IgG kappa in a patient sample, suggesting this could be daratumumab or another t-mab in the report. However, with the advent of novel antibody-based medications, identification via traditional laboratory methods has grown more complex. Teclistamab-cqyv is an IgG4 lambda T-cell engager bispecific antibody targeting B-cell maturation antigen (BCMA) and CD3 on T cells, used in relapsed and refractory multiple myeloma. The goal of this study was to determine if teclistamab could be detected on serum immunofixation and mass-fix. Methods Residual waste serum samples with no monoclonal protein via mass-fix (a MALDI-TOF based assay used in place of serum immunofixation) and variable polyclonal background were used to spike teclistamab (n=3). Briefly, one sample had total IgG < 500 mg/dL measured by nephelometry on a Siemens BNII (431 mg/dL, hypo gamma), a second sample had IgG within reference intervals (779 mg/dL, normal gamma) and the third sample had IgG > 1600 mg/dL (1950 mg/dL, polyclonal hypergamma). Each sample was divided into 3 aliquots and spiked with teclistamab (Tecvayli, Johnson &Johnson) obtained from the pharmacy, at final concentrations of 10, 20, and 40 mg/dL in the serum samples. The nine artificial samples were subjected to immunofixation electrophoresis (Sebia) and a new monoclonal protein study using mass-fix, a laboratory developed test. Results In the serum immunofixation experiments, a single discrete IgG lambda band was visible in the hypogamma and normal gamma samples (Table 1) when teclistamab was present at 20 mg/dL or 40 mg/dL. No bands were observed for the 10 mg/dL spike in hypos or normals. No teclistamab was detected at any concentration in the hypergamma sample. When mass-fix was performed, monoclonal protein spikes consistent with the expected mass of the two unique lambda light chains associated with teclistamab (22624Da and 22636Da) were identified in the hypo and normal gamma samples at the 3 concentrations tested: 10, 20, and 40 mg/dL. No mass-fix spikes were seen above the polyclonal spectra in the hypergamma samples. Conclusion The polyclonal background of immunoglobulins in a serum specimen plays a significant role in the identification of any monoclonal protein. Teclistamab is a new IgG lambda t-mab with potential to show up as an interference in both immunofixation and mass-fix, depending on the amount of polyclonal IgG present. Without positive identification, teclistamab presence could complicate interpretation of a patient’s response to treatment. This proof-of-concept study shows that mass-fix can detect smaller concentrations of teclistamab than immunofixation, therefore would be more prone to identifying this t-mab than labs employing the gel-based immunofixation method.

Abstract Background The diagnosis of monoclonal gammopathies relies on the detection of monoclonal immunoglobulins (M-proteins) in serum or urine. Mass-Fix utilizes matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) to detect and quantify M-proteins. This method employs immunoaffinity enrichment using antibodies against heavy chains (HC) and light chains (LC), followed by MS analysis to determine M-protein isotypes. Mass-Fix has also revealed novel M-protein characteristics, including LC glycosylation and fragmentation, facilitated by measuring the mass of LC. LC glycosylation is as an independent risk factor for disease progression of monoclonal gammopathy of undetermined significance (MGUS), while light chain fragments have been postulated as the origin of amyloid light chain (AL) plaques. Since Mass-Fix enriches intact immunoglobulins before dissociating LCs, it potentially enhances fragment detection. However, the precise nature and clinical significance of these fragments remain to be fully elucidated. Methods Mass-Fix serum results from Mayo Clinic patients tested from September 10, 2018, to October 1, 2024, were reviewed for the presence of M-protein and LC fragments. The frequency and the isotype of fragment LC fragments was determined in the M-protein positive cohort (n=15410). Patients diagnosed with either MGUS (n=6996), AL amyloidosis (n=315), or both (n=32) who had positive M-protein results on Mass-Fix, either prior to or within one month after the diagnosis, were included for a retrospective clinical association study of LC fragments and disease. To validate that these fragments were not artifacts of MS analysis, PAGE gel analysis and Western blots were performed using clinical residual serum from 9 patients: 2 IgG/kappa and 3 IgG/lambda patients with detectable LC fragments and 2 IgG/kappa and 2 IgG/lambda patients without fragments. Samples were purified using antibodies against gamma heavy chains and reduced with TCEP prior to gel electrophoresis and Western blot. Results Of the 15410 patients with monoclonal proteins detected by Mass-Fix, 2896 (18.7%) had detectable LC fragments; kappa fragments in 1533 and lambda fragments in 1363. Most often, the fragments were observed in pairs, with combined molecular weight typically equaled that of the full-length monoclonal LC present in the same sample. LC fragments were observed more frequently among patients diagnosed with AL amyloidosis (118/347=34%) compared to those without the diagnosis (685/6996=10%), with an odds ratio of 4.75 (95% CI, 3.75-6.01). PAGE with Coomassie blue staining revealed bands with sizes representing LC fragments in the five M-protein samples with detectable LC fragments on Mass-Fix, while no such bands observed in those without LC fragments. Western blot using anti-kappa or anti-lambda antibodies confirmed the identity of the bands with higher molecular weight as a fragment of LC in each of the IgG/kappa and IgG/lambda samples. Conclusion Mass-Fix is able to discriminate LC fragments from intact LC based on their sizes. The detection of LC fragments with Western blot without ionization suggests a biological origin rather than analytical artifacts from MS. The clinical association study suggests that LC fragments may have utility in increasing the suspicion of AL amyloidosis in M-protein positive patients with LC fragments, potentially facilitating earlier intervention and improving patient outcomes.

Abstract Purpose: To evaluate the association between neutrophil-to-lymphocyte ratio (NLR) and efficacy of avelumab plus axitinib or sunitinib. Experimental Design: Adult patients with untreated advanced renal cell carcinoma (RCC) with a clear-cell component, ≥1 measurable lesions, Eastern Cooperative Oncology Group performance status of 0 or 1, fresh or archival tumor specimen, and adequate renal, cardiac, and hepatic function were included. Retrospective analyses of the association between baseline NLR and progression-free survival (PFS) and overall survival (OS) in the avelumab plus axitinib or sunitinib arms were performed using the first interim analysis of the phase 3 JAVELIN Renal 101 trial (NCT02684006). Multivariate Cox regression analyses of PFS and OS were conducted. Translational data were assessed to elucidate the underlying biology associated with differences in NLR. Results: Patients with below-median NLR had longer observed PFS with avelumab plus axitinib [stratified HR, 0.85; 95% confidence interval (CI), 0.634–1.153] or sunitinib (HR, 0.56; 95% CI, 0.415–0.745). In the avelumab plus axitinib or sunitinib arms, respectively, median PFS was 13.8 and 11.2 months in patients with below-median NLR, and 13.3 and 5.6 months in patients with median-or-higher NLR. Below-median NLR was also associated with longer observed OS in the avelumab plus axitinib (HR, 0.51; 95% CI, 0.300–0.871) and sunitinib arms (HR, 0.30; 95% CI, 0.174–0.511). Tumor analyses showed an association between NLR and key biological characteristics, suggesting a role of NLR in underlying mechanisms influencing clinical outcome. Conclusions: Current data support NLR as a prognostic biomarker in patients with advanced RCC receiving avelumab plus axitinib or sunitinib.

10006 Background: Treatment options are limited for patients with advanced melanoma who have progressed on checkpoint inhibitors and targeted therapies. Adoptive cell therapy using tumor-infiltrating lymphocytes (TIL) leverages and enhances the body’s natural defense against cancer and has shown durable responses in heavily pretreated melanoma patients. Methods: C-144-01 is a global Phase 2 open-label, multicenter study of efficacy & safety of lifileucel in patients with unresectable metastatic melanoma who have progressed on checkpoint inhibitors and BRAF/MEK inhibitors, if BRAFv600 mutant. We report on Cohort 2 (N = 66) patients who have received TIL. Tumors were resected at local institutions, processed in central GMP facilities for TIL production, manufactured, cryopreserved & shipped back to sites in a 22-day process. Therapy consisted of one week of lymphodepletion, a single lifileucel infusion, and up to 6 IL-2 doses. ORR was based on RECIST v1.1 by investigator assessment. Data cutoff was Feb 2, 2020. Results: Baseline characteristics: 3.3 mean prior therapies (anti-PD1 100%; anti-CTLA-4 80%; BRAF/MEK inhibitor 23%), high baseline tumor burden (106 mm mean target lesion sum of diameters), 44% liver/brain lesions, 40.9% LDH > ULN. ORR by investigator was 36.4% (2 CR, 22 PR) and DCR was 80.3%. Mean time to response was 1.9 months (range: 1.3-5.6). After a median study follow-up of 17.0 months, median DOR (mDOR) was still not reached. Six responders have progressed, 2 have died and 2 started other anti-cancer therapy without progression. The adverse event profile was consistent with the underlying advanced disease and the lymphodepletion and IL-2 regimens. Additional follow-up data will be available for presentation. Conclusions: Lifileucel treatment results in a 36.4% ORR and mDOR was not reached at 17.0 months of median study follow up in a heavily pretreated metastatic melanoma patients with high baseline disease burden who progressed on multiple prior therapies, including anti-PD1 and BRAF/MEK inhibitors, if BRAFv600 mutant. Clinical trial information: NCT02360579.

5061 Background: The phase 3 JAVELIN Renal 101 trial (NCT02684006) in treatment-naive patients with advanced renal cell carcinoma (aRCC) demonstrated significantly improved progression-free survival (PFS; hazard ratio [HR], 0.69; 95% CI, 0.56, 0.84; P < 0.001) and higher objective response rate (ORR; 51.4% vs 25.7%) with avelumab + axitinib vs sunitinib (Motzer RJ, et al. N Engl J Med. 2019;380:1103-15). NLR has emerged as a potential prognostic biomarker in aRCC; elevated NLR is associated with poorer prognosis. Here, we describe the association of NLR with the efficacy of avelumab + axitinib from JAVELIN Renal 101. Methods: We examined baseline NLR and its association with efficacy outcomes. PFS, best overall response (per blinded independent central review using RECIST 1.1), and overall survival (OS) data from the avelumab + axitinib arm from the first interim analysis of JAVELIN Renal 101 were analyzed (data cutoff, June 20, 2018). Multivariate Cox regression analyses of PFS and OS were also conducted. Results: In the avelumab + axitinib arm, patients with < median NLR (N = 217) had longer observed PFS (stratified HR, 0.85; 95% CI, 0.634, 1.153) and longer observed OS (stratified HR, 0.51; 95% CI, 0.300, 0.871) than patients with ≥ median NLR (N = 217). The ORR was 57.1% in patients with < median NLR vs 47.5% in patients with ≥ median NLR, with complete response in 5.5% vs 1.4%. Multivariate analysis showed that low NLR was associated with longer PFS and OS by treating baseline NLR as either a continuous variable or a binary variable (dichotomized by median). Conclusions: Low NLR was associated with better observed treatment outcomes in patients with aRCC who received avelumab + axitinib. Clinical trial information: NCT02684006 .

Receptor molecules play a major role in the desensitization of agonist-stimulated cellular responses. For G protein-coupled receptors, rapid desensitization occurs via receptor phosphorylation, sequestration, and internalization, yet the cellular compartments in which these events occur and their interrelationships are unclear. In this work, we focus on the cholecystokinin (CCK) receptor, which has been well characterized with respect to phosphorylation. We have used novel fluorescent and electron-dense CCK receptor ligands and an antibody to probe receptor localization in a CCK receptor-bearing CHO cell line. In the unstimulated state, receptors were diffusely distributed over the plasmalemma. Agonist occupation stimulated endocytosis via both clathrin-dependent and independent pathways. The former was predominant, leading to endosomal and lysosomal compartments, as well as recycling to the plasmalemma. The clathrin-independent processes led to a smooth vesicular compartment adjacent to the plasmalemma resembling caveolae, which did not transport ligand deeper within the cell. Potassium depletion largely eliminated clathrin-dependent endocytosis, while not interfering with agonist-stimulated receptor movement into subplasmalemmal smooth vesicle compartments. These cellular endocytic events can be related to the established cycle of CCK receptor phosphorylation and dephosphorylation, which we have previously described (Klueppelberg, U. G., L. K. Gates, F. S. Gorelick, and L. J. Miller. 1991. J. Biol. Chem. 266:2403-2408; Lutz, M. P., D. I. Pinon, L. K. Gates, S. Shenolikar, and L. J. Miller. 1993. J. Biol. Chem. 268:12136-12142). The rapid onset and peak of receptor phosphorylation after agonist occupation correlates best with a plasmalemmal localization, while stimulated receptor phosphatase activity correlates best with receptor residence in intracellular compartments. We postulate that the smooth vesicular compartment adjacent to the plasmalemma functions for the rapid resensitization of the receptor, while the classical clathrin-mediated endocytotic pathway is key for receptor downregulation via lysosomal degradation, as well as less rapid resensitization.