A Biomarker Obtained From Whole Peripheral Blood Predicts Response to Bortezomib: Results of a Multicenter Prospective Clinical Study of Multiple Myeloma in Japan.
Authors: Watanabe Takashi , Mitsuhashi Masato , Sagawa Morihiko , Suzuki Kenshi , Ri Masaki , Abe Masahiro , Ohmachi Ken , Nakagawa Yasunori , Nakamura Shingen , Chosa Mizuki , Iida Shinsuke , Kizaki Masahiro 
Published: October 2019

Abstract
Abstract 2954

Introduction:
The first-in-class proteasome inhibitor bortezomib (Bzb) has revolutionized the treatment of multiple myeloma (MM). However, identifying a biomarker to predict which patients will respond to Bzb is a priority in selecting this treatment or determining whether this powerful but toxic armament should be continued in individual patients. Furthermore, to monitor the efficacy of Bzb, peripheral blood (PB) biomarkers are more desirable than painful bone marrow aspirations.

Methods:
We conducted a multicenter prospective study to seek biomarkers that predict a response to Bzb. Patients with previously treated or untreated symptomatic MM received twice-weekly or weekly doses of 1.3 mg/m2 Bzb with or without dexamethasone. All patients had measurable M-protein levels. All patients provided written informed consent. Review boards at each site approved the study, which was conducted in accordance with the Declaration of Helsinki. A 2 ml sample of heparinized whole blood was obtained before treatment, as well as 2–3 days and 1–2 weeks after i.v. administration of the first dose of Bzb treatment in the 1st cycle. Triplicate aliquots of 0.06 ml of whole blood were mixed with phytohemaglutinin (PHA), heat-aggregated IgG (HAG), lipopolysaccharide (LPS), zymosan A (ZA), or solvent phosphate buffered saline (PBS) and incubated for 4 hours at 37°C. After incubation, the samples were stored at −80°C. The levels of the target mRNAs (IL2, IFNγ, GMCSF, TNFα, CCL4, IL6, CXCL10, and control ACTB) were quantified from each aliquot using a previously described method (J Immunol Methods 363: 95, 2010). The analysis of mRNA and collection of clinical data were performed separately at different centers. Clinical response was assessed according to the International Uniform Response Criteria.

Results:
Between March 2010 and March 2012, a total of 64 patients (33 male and 31 female) were enrolled from 6 centers. The median age of all patients was 62 years. The original protocol stipulated that only relapsed or refractory patients were eligible, but in October 2011, the protocol was amended to include newly diagnosed patients due to changes in the Japanese National Health Insurance policy. Consequently, 42 patients were previously treated and 22 patients were untreated. After excluding 1 patient who died early from progressive disease and 1 who received additional treatment, 62 patients were eligible for response analysis. Five patients achieved CR and VGPR, 25 patients obtained PR and SD, and 2 cases of PD were documented. The median follow-up time of estimable patients was 160.5 (range, 26 to 666) days. A total of 2,444 (64 [patients] × 5 [stimulants] × 3 [triplicate] × 3 [time points] with some sampling failure subtracted) mRNA/cDNA samples were prepared, and 19,552 (2,444 [cDNA] × 8 [mRNAs]) PCRs were performed. In total, 53 patient blood samples qualified for mRNA analysis. Among the 32 sample dataset (4 stimulants × 8 mRNAs) obtained before Bzb treatment, LPS-induced CXCL10 correlated with clinical responses, where 9 out of 10 cases of CR and VGPR showed a >=3 fold increase (FI), and both cases of PD showed an FI <3. The FI of PR and SD was distributed widely without a clear distinction. Moreover, after administration of Bzb, LPS-induced CXCL10 declined to less than 30% in all cases of CR and VGPR, whereas PR and SD had mixed results. Interestingly, 7 out of 10 CR and VGPR cases maintained the suppression of LPS-induced CXCL10, even after 1–2 weeks.

Conclusion:
LPS-induced CXCL10 mRNA in peripheral whole blood is a promising biomarker for the prediction and monitoring of CR and VGPR responses to Bzb treatment.

Disclosures:
Mitsuhashi: the company who owns the technology of mRNA analysis used in this study: Employment. Abe:Janssen Pharmaceutical K.K.: Honoraria, Research Funding. Nakagawa:Janssen Pharmaceutical K.K.: Honoraria. Nakamura:Janssen Pharmaceutical K.K.: Honoraria. Iida:Janssen Pharmaceutical K.K.: Honoraria. Kizaki:Janssen Pharmaceutical K.K.: Honoraria.