Cerdulatinib Pharmacodynamics and Relationships to Tumor Response Following Oral Dosing in Patients with Relapsed/Refractory B-cell Malignancies

PURPOSE

Preclinical studies suggest SYK and JAK contribute to tumor-intrinsic and microenvironment-derived survival signals. The pharmacodynamics of cerdulatinib, a dual SYK/JAK inhibitor, and associations with tumor response were investigated.

PATIENTS AND METHODS

In a phase I dose-escalation study in adults with relapsed/refractory B-cell malignancies, cerdulatinib was administered orally to sequential dose-escalation cohorts using once-daily or twice-daily schedules. The study enrolled 8 patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), 13 with follicular lymphoma, 16 with diffuse large B-cell lymphoma (DLBCL), and 6 with mantle cell lymphoma. Correlation of tumor response with pharmacodynamic markers was determined in patients with meaningful clinical responses.

RESULTS

Following cerdulatinib administration, complete SYK and JAK pathway inhibition was achieved in whole blood of patients at tolerated exposures. Target inhibition correlated with serum cerdulatinib concentration, and IC₅₀ values against B-cell antigen receptor (BCR), IL2, IL4, and IL6 signaling pathways were 0.27 to 1.11 μmol/L, depending on the phosphorylation event. Significant correlations were observed between SYK and JAK pathway inhibition and tumor response. Serum inflammation markers were reduced by cerdulatinib, and several significantly correlated with tumor response. Diminished expression of CD69 and CD86 (B-cell activation markers), CD5 (negative regulator of BCR signaling), and enhanced expression of CXCR4 were observed in 2 patients with CLL, consistent with BCR and IL4 suppression and loss of proliferative capacity.

CONCLUSIONS

Cerdulatinib potently and selectively inhibited SYK/JAK signaling at tolerated exposures in patients with relapsed/refractory B-cell malignancies. The extent of target inhibition in whole-blood assays and suppression of inflammation correlated with tumor response. (ClinicalTrials.gov ID:NCT01994382).

Abstract 305: Cerdulatinib induces Bim expression and synergistic cell kill in combination with venetoclax in follicular lymphoma cell lines

Follicular lymphoma (FL) is the most frequently occurring indolent B-cell non-Hodgkin lymphoma. Treatment typically involves rituximab in combination with bendamustine, CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone), or CVP (cyclophosphamide, vincristine, and prednisone). Disease relapse is high, and current treatment options for these patients are limited. BTK inhibition has limited clinical activity in FL patients, and while the PI3Kδ inhibitor idelalisib was recently approved, tolerability has been an issue. Limited clinical activity was observed with the Bcl-2 inhibitor venetoclax, due to a compensatory upregulation of Mcl-1 by the tumor cell. Consequently, novel treatment strategies are required for patients with relapsed/refractory FL. Cerdulatinib is a dual SYK/JAK inhibitor that targets the BCR and cytokine signaling pathways. We previously demonstrated in chronic lymphocytic leukemia (CLL) cells that cerdulatinib inhibited signaling via the BCR and IL-4 signaling pathways and induced apoptosis in a dose- and time-dependent manner. However, the mechanism behind cerdulatinib-induced tumor killing has not previously been investigated. Herein we explore the function of cerdulatinib alone and in combination with venetoclax for the treatment of FL. To confirm cerdulatinib activity in FL derived cells lines WSU-FSCCL, DOHH2 and SU-DHL6, cells were incubated with cerdulatinib prior to BCR or cytokine receptor engagement. Cerdulatinib (0.1-1µM) significantly inhibited anti-Ig-induced pAKTS473, pERKThr202/Tyr204, pS6 ribosomal subunit Ser235/236 and cytokine-induced STAT signaling. The Bcl-2 protein was highly expressed in all cell lines consistent with a t(14:18) translocation, whereas basal Mcl-1 was expressed at lower levels. Bcl-2 levels remained unchanged following cerdulatinib treatment in all three cell lines. However, in contrast to CLL where cerdulatinib inhibited Mcl-1 expression, modulation of Mcl-1 protein expression by cerdulatinib in FL cell lines was subtle and inconsistent. Cerdulatinib alone induced 12%-44% cell death in all cell lines tested in a time dependent manner (24-72h) and this correlated with a robust increase in Bim expression at the RNA and protein level. We subsequently treated DOHH2, WSU-FSCCL and DHL6 cells with cerdulatinib in combination with 10-100nM venetoclax. Venetoclax synergized with cerdulatinib to induce significantly greater levels of apoptosis in all cell lines investigated compared to either agent alone and appeared to function by displacing Bim from Bcl-2. To demonstrate in vivo capability, we xenografted SU-DHL6 subcutaneously in nude mice. Cerdulatinib in combination with venetoclax led to greater antitumor activity when compared to vehicle or either drug alone. Together these data highlight a rationale for combining cerdulatinib with venetoclax for the treatment of FL.

Citation Format: Andrew J. Steele, Greg Coffey, JiaJia Feng, Matthew D. Blunt, Francis DeGuzman, Deogracias Canivel, Jack Rose, Kenneth Der, Janet Leeds, Anjali Pandey, Pamela Conley. Cerdulatinib induces Bim expression and synergistic cell kill in combination with venetoclax in follicular lymphoma cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 305.

The role of liver and kidney on the pharmacokinetics of a recombinant amino terminal fragment of bactericidal/permeability-increasing protein in rats

PURPOSE

The pharmacokinetics of rBPI23, a recombinant amino terminal fragment of bactericidal/permeability-increasing protein that binds to and neutralizes endotoxin, was investigated.

METHODS

rBPI23 was administered to rats at doses 0.01-10 mg/kg and plasma rBPI23 levels were measured by ELISA. rBPI23 was also administered to bilaterally nephrectomized rats. In addition, rBPI23 was administered intra-hepatically via the pyloric vein to determine the first-pass effect by the liver. rBPI23 concentrations were also simultaneously measured in the right atrium and aorta to determine the removal of rBPI23 by the lungs.

RESULTS

The concentration-time profile of rBPI23 was described by a 3-compartmental model with parallel first order and Michaelis-Menten (saturable) elimination. The clearance of rBPI23 was not altered by bilateral nephrectomy. Clearance of intra-hepatically administered rBPI23 was 4.5 fold lower than intra-femorally administered rBPI23. The concentration difference of rBPI23 between aortic and right atrial blood was no greater than 11%. Clearance of rBPI23 in rats could be reduced up to 10 fold by co-administration of heparin. Uptake by liver of intra-hepatically administered rBPI23 was prevented by co-administration of heparin.

CONCLUSIONS

rBPI23 is not significantly cleared by the kidneys, and no more than 11% of the rBPI23 was removed by the lungs with each pass. The liver could remove 78% of the rBPI23 from the hepatic circulation. Studies with heparin suggest rBPI23 is cleared by binding to heparan sulfate sites in the liver.

Biochemical characterization of recombinant fusions of lipopolysaccharide binding protein and bactericidal/permeability-increasing protein. Implications in biological activity

The physiological response to endotoxin (lipopolysaccharide (LPS)) can be regulated by two closely related LPS-binding proteins, LPS-binding protein (LBP), which potentiates LPS' inflammatory activity via interaction with the monocytic antigen CD14, and bactericidal/permeability-increasing protein (BPI), which neutralizes LPS. Both proteins bind LPS with high affinity sites in their N-terminal domains, whereas interaction between LBP and CD14 is dependent upon the LBP C-terminal domain. We have created fusions of the N- and C-terminal domains from each protein and compared the functional activities and pharmacokinetics of these fusions, the individual N-terminal domains, and the parent proteins. The N-terminal domains of BPI and LBP bound lipid A with their characteristic apparent affinity constants, regardless of the C-terminal fusion partner. In addition, the C-terminal domain of LBP allowed transfer of LPS to CD14 in conjunction with either N-terminal LPS binding domain. Proteins containing a BPI N-terminal domain had greater heparin binding capacities in vitro and were cleared more rapidly from the plasma of whole animals. Taken together, these data better define how closely related proteins such as BPI and LBP can have opposing effects on the body's response to LPS.

Alteration of the pharmacokinetics of small proteins by iodination

The pharmacokinetics of several proteins were investigated using two different assays. A 23 kDa recombinant protein fragment of bactericidal/permeability-increasing protein (rBPI23) was radiolabeled with 125I using Iodo-beads and administered rats. Plasma samples were collected and assayed for 125I-rBPI23 by radioactivity. In a separate experiment, rBPI23 was administered to rats and plasma samples were assayed for rBPI23 by ELISA. The clearance determined from plasma concentrations of 125I-rBPI23 measured by radioactivity was about 2.5-fold lower than that of rBPI23 determined by ELISA. In addition, the steady state volumes of distribution and mean residence times of 125I-rBPI23 measured by radioactivity were four-fold and 10-fold greater, respectively, compared to those measured by the ELISA method. By studying several proteins with a range of molecular weights, we found that the pharmacokinetics of proteins below about 60 kDa were different when assayed by radioactivity or ELISA, but those of proteins with molecular weights of at least 80 kDA revealed only minor differences. To determine which assay method yielded the correct plasma pharmacokinetic profile, rBPI23 was metabolically labeled with 35S-methionine and administered to rats, and plasma samples were assayed by radioactivity. The concentration-time profile assessed by this method was very close to that determined by ELISA. Exposing rBPI23 to chloramine-T (the oxidant used in the iodination process) and measuring its plasma concentration by ELISA revealed pharmacokinetics similar to those of the iodinated protein measured by radioactivity. In contrast, radiolabeling rBPI23 using iodinated Bolton-Hunter reagent (which avoids exposing the protein to oxidant), and measuring 125I-rBPI23 by radioactivity, yielded pharmacokinetics that were similar, although not identical, to the pharmacokinetics of rBPI23 measured by ELISA. Thus, our data suggest that directly iodinating low-molecular-weight proteins by oxidation procedures alters their clearance from the blood, preventing reliable determination of pharmacokinetic parameters.