Characterization of CD33/CD3 Tetravalent Bispecific Tandem Diabodies (TandAbs) for the Treatment of Acute Myeloid Leukemia.

PURPOSE: Randomized studies with gemtuzumab ozogamicin have validated CD33 as a target for antigen-specific immunotherapy of acute myelogenous leukemia (AML). Here, we investigated the potential of CD33/CD3-directed tandem diabodies (TandAbs) as novel treatment approach for AML. These tetravalent bispecific antibodies provide two binding sites for each antigen to maintain the avidity of a bivalent antibody and have a molecular weight exceeding the renal clearance threshold, thus offering a longer half-life compared to smaller antibody constructs. EXPERIMENTAL DESIGN: We constructed a series of TandAbs composed of anti-CD33 and anti-CD3 variable domains of diverse binding affinities and profiled their functional properties in CD33+ human leukemia cell lines, xenograft models, and AML patient samples. RESULTS: Our studies demonstrated that several CD33/CD3 TandAbs could induce potent, dose-dependent cytolysis of CD33+ AML cell lines. This effect was modulated by the effector-to-target cell ratio and strictly required the presence of T cells. Activation and proliferation of T cells and maximal AML cell cytolysis correlated with high avidity to both CD33 and CD3. High-avidity TandAbs were broadly active in primary specimens from patients with newly diagnosed or relapsed/refractory AML in vitro, with cytotoxic properties independent of CD33 receptor density and cytogenetic risk. Tumor growth delay and inhibition were observed in both prophylactic and established HL-60 xenograft models in immunodeficient mice. CONCLUSIONS: Our data show high efficacy of CD33/CD3 TandAbs in various preclinical models of human AML. Together, these findings support further study of CD33/CD3 TandAbs as novel immunotherapeutics for patients with AML. Clin Cancer Res; 22(23); 5829-38. ©2016 AACR.

Modeling absolute lymphocyte counts after treatment of chronic lymphocytic leukemia with ibrutinib.

The objective in this study was to characterize the pattern of the treatment-related lymphocytosis curve in chronic lymphocytic leukemia (CLL) patients treated with ibrutinib, and assess the relationship between the baseline factors and absolute lymphocyte counts (ALC). The PCYC-1102-CA study was a five-arm phase Ib/II open-label, nonrandomized, multicenter study in CLL/SLL. The arms and accruals were 420 and 840 mg/day treatment-naive elderly CLL/SLL (N = 27 and N = 4, respectively), 420 and 840 mg/day relapsed/refractory CLL/SLL (N = 27 and N = 34, respectively), and 420 mg/day high-risk CLL/SLL (N = 24). The results were generated through statistical modeling using data from a clinical trial (PCYC-1102) in five cohorts of treatment-naïve or relapsed/refractory CLL patients treated at 420 and 840 mg daily of ibrutinib. In cases in which the initial increase in ALC doubles by day 28, it takes patients longer to reach their maximum ALC when compared with those with a lower rate of increase. Our models show that all of the cohorts exhibited the same pattern of treatment-related lymphocytosis from ibrutinib, and there are no significant differences between cohorts, including no detectable dose effect. The ALC of the majority of patients return to baseline ALC values by the end of cycle 5.

Active idiotypic vaccination versus control immunotherapy for follicular lymphoma.

PURPOSE: Idiotypes (Ids), the unique portions of tumor immunoglobulins, can serve as targets for passive and active immunotherapies for lymphoma. We performed a multicenter, randomized trial comparing a specific vaccine (MyVax), comprising Id chemically coupled to keyhole limpet hemocyanin (KLH) plus granulocyte macrophage colony-stimulating factor (GM-CSF) to a control immunotherapy with KLH plus GM-CSF. PATIENTS AND METHODS: Patients with previously untreated advanced-stage follicular lymphoma (FL) received eight cycles of chemotherapy with cyclophosphamide, vincristine, and prednisone. Those achieving sustained partial or complete remission (n=287 [44%]) were randomly assigned at a ratio of 2:1 to receive one injection per month for 7 months of MyVax or control immunotherapy. Anti-Id antibody responses (humoral immune responses [IRs]) were measured before each immunization. The primary end point was progression-free survival (PFS). Secondary end points included IR and time to subsequent antilymphoma therapy. RESULTS: At a median follow-up of 58 months, no significant difference was observed in either PFS or time to next therapy between the two arms. In the MyVax group (n=195), anti-Id IRs were observed in 41% of patients, with a median PFS of 40 months, significantly exceeding the median PFS observed in patients without such Id-induced IRs and in those receiving control immunotherapy. CONCLUSION: This trial failed to demonstrate clinical benefit of specific immunotherapy. The subset of vaccinated patients mounting specific anti-Id responses had superior outcomes. Whether this reflects a therapeutic benefit or is a marker for more favorable underlying prognosis requires further study.

Targeting BTK with ibrutinib in relapsed or refractory mantle-cell lymphoma.

BACKGROUND: Bruton's tyrosine kinase (BTK) is a mediator of the B-cell-receptor signaling pathway implicated in the pathogenesis of B-cell cancers. In a phase 1 study, ibrutinib, a BTK inhibitor, showed antitumor activity in several types of non-Hodgkin's lymphoma, including mantle-cell lymphoma. METHODS: In this phase 2 study, we investigated oral ibrutinib, at a daily dose of 560 mg, in 111 patients with relapsed or refractory mantle-cell lymphoma. Patients were enrolled into two groups: those who had previously received at least 2 cycles of bortezomib therapy and those who had received less than 2 complete cycles of bortezomib or had received no prior bortezomib therapy. The primary end point was the overall response rate. Secondary end points were duration of response, progression-free survival, overall survival, and safety. RESULTS: The median age was 68 years, and 86% of patients had intermediate-risk or high-risk mantle-cell lymphoma according to clinical prognostic factors. Patients had received a median of three prior therapies. The most common treatment-related adverse events were mild or moderate diarrhea, fatigue, and nausea. Grade 3 or higher hematologic events were infrequent and included neutropenia (in 16% of patients), thrombocytopenia (in 11%), and anemia (in 10%). A response rate of 68% (75 patients) was observed, with a complete response rate of 21% and a partial response rate of 47%; prior treatment with bortezomib had no effect on the response rate. With an estimated median follow-up of 15.3 months, the estimated median response duration was 17.5 months (95% confidence interval [CI], 15.8 to not reached), the estimated median progression-free survival was 13.9 months (95% CI, 7.0 to not reached), and the median overall survival was not reached. The estimated rate of overall survival was 58% at 18 months. CONCLUSIONS: Ibrutinib shows durable single-agent efficacy in relapsed or refractory mantle-cell lymphoma. (Funded by Pharmacyclics and others; ClinicalTrials.gov number, NCT01236391.)

Phase Ib dose-escalation study (PX-171-006) of carfilzomib, lenalidomide, and low-dose dexamethasone in relapsed or progressive multiple myeloma.

PURPOSE: Carfilzomib, a selective proteasome inhibitor, has shown safety and efficacy in relapsed and/or refractory multiple myeloma. This phase I study in patients with relapsed or progressive multiple myeloma assessed the safety and tolerability of escalating doses of carfilzomib in combination with lenalidomide and low-dose dexamethasone (CRd) to identify the dose for a phase II expansion study. EXPERIMENTAL DESIGN: Patients with multiple myeloma who relapsed after 1 to 3 prior regimens enrolled into dose-escalation cohorts. CRd was administered on 28-day dosing cycles: carfilzomib 15 to 27 mg/m(2) on days 1, 2, 8, 9, 15, and 16; lenalidomide 10 to 25 mg on days 1 to 21; and dexamethasone 40 mg weekly. RESULTS: Forty patients enrolled in six cohorts. Prior treatment included bortezomib (75%) and lenalidomide (70%); 20% and 36% were refractory overall. The maximum tolerated dose was not identified, and the highest dose combination tested was recommended for the phase II study. The most common toxicities of any grade were fatigue (62.5%), neutropenia (55.5%), and diarrhea (52.5%). Grade 3/4 toxicities included neutropenia (42.5%), thrombocytopenia (32.5%), and lymphopenia (27.5%), with no grade 3/4 neuropathy reported. Proteasome inhibition 1-hour after dose was more than 80% in cycles 1 and 2. Among all patients, the overall response rate was 62.5%, the clinical benefit response rate was 75.0%, and the median duration of response and progression-free survival were 11.8 and 10.2 months, respectively. CONCLUSION: The maximum planned CRd dose, carfilzomib 27 mg/m(2), lenalidomide 25 mg, and dexamethasone 40 mg, was recommended for further study, with promising safety and efficacy.

An open-label single-arm pilot phase II study (PX-171-003-A0) of low-dose, single-agent carfilzomib in patients with relapsed and refractory multiple myeloma.

UNLABELLED: An open-label single-arm multicenter pilot phase II study of the next-generation selective proteasome inhibitor carfilzomib was conducted in 46 patients with relapsed and refractory multiple myeloma (MM) after ≥ 2 previous therapies. The best overall response rate (ORR) was 16.7%, with a median duration of response of 7.2 months. This pilot study was the first phase II single-agent trial conducted with carfilzomib. BACKGROUND: Carfilzomib is a next-generation selective proteasome inhibitor that irreversibly binds its target and has demonstrated single-agent activity in patients with bortezomib-resistant multiple myeloma (MM). PX-171-003-A0, an open-label single-arm multicenter pilot phase II study, enrolled 46 patients with relapsed MM after ≥ 2 previous therapies including bortezomib and an immunomodulator (thalidomide or lenalidomide) and disease refractory to the last treatment regimen preceding study entry. METHODS: Patients received carfilzomib 20 mg/m(2) intravenously on days 1, 2, 8, 9, 15, and 16 every 28 days for up to 12 cycles. Responses in 42 evaluable patients were assessed per International Myeloma Working Group Uniform Response Criteria, with minimal response assessed per European Group for Blood and Marrow Transplantation (EBMT) criteria. RESULTS: The primary endpoint of best ORR was 16.7%, including 7 partial responses. Median duration of response was 7.2 months. Clinical benefit response (CBR) rate was 23.8% with a median duration of response of 13.8 months. The most common treatment-emergent adverse events (AEs) of any grade were anemia (73.9%), fatigue (69.6%), and thrombocytopenia (50.0%). Notably, peripheral neuropathy and neuropathy-related AEs were generally mild and infrequent. CONCLUSION: This pilot study was the first phase II single-agent trial conducted with carfilzomib. Based on these findings, the study was amended to test a higher carfilzomib dose in an additional 250 patients (PX-171-003-A1).

An open-label, single-arm, phase 2 study of single-agent carfilzomib in patients with relapsed and/or refractory multiple myeloma who have been previously treated with bortezomib.

Carfilzomib is a next-generation proteasome inhibitor that selectively and irreversibly binds to its target. In clinical studies, carfilzomib has shown efficacy in patients with relapsed and/or refractory multiple myeloma (MM) and has demonstrated a tolerable safety profile. In this phase 2, open-label, multicentre clinical trial, 35 patients with relapsed and/or refractory MM following 1-3 prior therapies, including at least one bortezomib-based regimen, received carfilzomib 20 mg/m(2) in a twice-weekly, consecutive-day dosing schedule for ≤12 monthly cycles. The best overall response rate (ORR) was 17·1% and the clinical benefit response rate (ORR + minimal response) was 31·4%. The median duration of response was >10·6 months and the median time to progression was 4·6 months. The most common adverse events were fatigue (62·9%), nausea (60·0%), and vomiting (42·9%). No exacerbation of baseline peripheral neuropathy was observed. Single-agent carfilzomib was generally well tolerated for up to 12 treatment cycles and showed activity in patients with relapsed and/or refractory MM who had received prior treatment with bortezomib. These data, combined with an acceptable toxicity profile, support the potential use of carfilzomib in patients with relapsed and/or refractory MM and warrant continued investigation of carfilzomib as single agent or in combination with other agents.

A phase I single-agent study of twice-weekly consecutive-day dosing of the proteasome inhibitor carfilzomib in patients with relapsed or refractory multiple myeloma or lymphoma.

PURPOSE: Carfilzomib is a next-generation, selective, proteasome inhibitor with clinical activity in relapsed and/or refractory multiple myeloma. The objectives of this phase I study were to establish the safety, tolerability, pharmacokinetic, and pharmacodynamic profiles of escalating doses of carfilzomib in patients with relapsed or refractory hematologic malignancies. EXPERIMENTAL DESIGN: Carfilzomib (doses ranging from 1.2-27 mg/m(2)) was administered i.v. on 2 consecutive days for 3 weeks of a 4-week cycle. Single-agent dose escalation (n = 37) was followed by a dose-expansion phase (n = 11) that comprised 2 cohorts (carfilzomib or carfilzomib + dexamethasone). During dose expansion, carfilzomib was administered starting with 20 mg/m(2) during the first week (days 1, 2) and then escalated to 27 mg/m(2) thereafter. RESULTS: A maximum tolerated dose (MTD) was not reached during dose escalation. Dosing in the expansion cohort was well tolerated. Adverse events were manageable and primarily of grade I or II. The main hematologic adverse events of ≥ grade III were anemia and thrombocytopenia. Notably, there were no observations of grade III or more peripheral neuropathy. Carfilzomib was cleared rapidly with an elimination half-life of less than 30 minutes but still induced dose-dependent inhibition of the 20S chymotrypsin-like proteasome activity. At doses of 15 to 27 mg/m(2), there was evidence of activity among patients with multiple myeloma and with non-Hodgkin lymphoma. CONCLUSIONS: Escalated dosing of carfilzomib on a schedule of 2 consecutive days for 3 weeks of a 4-week cycle was tolerable and showed promising activity. This dose regimen has been selected for ongoing and future clinical studies, including PX-171-003A1 and the pivotal trial ASPIRE.

An open-label, single-arm, phase 2 (PX-171-004) study of single-agent carfilzomib in bortezomib-naive patients with relapsed and/or refractory multiple myeloma.

Carfilzomib is a selective proteasome inhibitor that binds irreversibly to its target. In phase 1 studies, carfilzomib elicited promising responses and an acceptable toxicity profile in patients with relapsed and/or refractory multiple myeloma (R/R MM). In the present phase 2, multicenter, open-label study, 129 bortezomib-naive patients with R/R MM (median of 2 prior therapies) were separated into Cohort 1, scheduled to receive intravenous carfilzomib 20 mg/m(2) for all treatment cycles, and Cohort 2, scheduled to receive 20 mg/m(2) for cycle 1 and then 27 mg/m(2) for all subsequent cycles. The primary end point was an overall response rate (≥ partial response) of 42.4% in Cohort 1 and 52.2% in Cohort 2. The clinical benefit response (overall response rate + minimal response) was 59.3% and 64.2% in Cohorts 1 and 2, respectively. Median duration of response was 13.1 months and not reached, and median time to progression was 8.3 months and not reached, respectively. The most common treatment-emergent adverse events were fatigue (62.0%) and nausea (48.8%). Single-agent carfilzomib elicited a low incidence of peripheral neuropathy-17.1% overall (1 grade 3; no grade 4)-in these pretreated bortezomib-naive patients. The results of the present study support the use of carfilzomib in R/R MM patients. This trial is registered at www.clinicaltrials.gov as NCT00530816.

Phase 1 experience with an anti-glycotope monoclonal antibody, RAV12, in recurrent adenocarcinoma.

PURPOSE: RAV12 is a high affinity, internalizing, chimeric IgG1 monoclonal antibody that binds RAAG12, a novel primate-restricted N-linked carbohydrate epitope present on multiple cell surface proteins. RAAG12 is highly expressed on many adenocarcinomas, particularly those of gastrointestinal origin. A phase 1 dose-escalation safety and pharmacokinetics trial was conducted in patients with metastatic or recurrent adenocarcinomas. EXPERIMENTAL DESIGN: RAV12 was initially given i.v. weekly x4, then by fractionated dosing twice or thrice weekly. Thirty-three patients were treated in the dose escalation segment of the trial in the following cohorts: 0.3 mg/kg qw (6), 1.0 mg/kg qw (8), 1.5 mg/kg qw (7); and 0.5 mg/kg biw (3), 0.75 mg/kg biw (3), and 0.5 mg/kg tiw (6). Twenty patients were enrolled in a maximum tolerated dose cohort expansion at 0.75 mg/kg biw. RESULTS: Two clinical syndromes were associated with drug administration: abdominal cramping pain with diarrhea, and asymptomatic, self-limited increases of liver function tests. These effects were partially ameliorated with fractionated dosing. Pharmacokinetics was dose dependent. Maximum concentration was reduced, whereas area under the concentration versus time curve was maintained with fractionated dosing. One patient with colorectal cancer experienced a durable partial remission, with a time to progression (TTP) of >8 months. Three additional patients experienced a TTP of >4 months. CONCLUSIONS: RAV12 has activity in recurrent adenocarcinomas. However, the safety profile of the antibody seems to preclude the delivery of highly efficacious doses. Re-engineering the molecule to remove FcRn binding (while maintaining FcgammaR binding) and to humanize it may improve the toxicity profile and efficacy.

A phase 1 dose escalation study of the safety and pharmacokinetics of the novel proteasome inhibitor carfilzomib (PR-171) in patients with hematologic malignancies.

PURPOSE: Carfilzomib (formerly PR-171) is a novel proteasome inhibitor of the epoxyketone class that is selective and structurally distinct from bortezomib. Proteasome inhibition by carfilzomib is mechanistically irreversible. Consequently, proteasome inhibition is more sustained with carfilzomib than with bortezomib. EXPERIMENTAL DESIGN: In a phase 1 trial evaluating the safety and efficacy of carfilzomib in relapsed or refractory hematologic malignancies, eight dose groups of three to six patients received 5 consecutive days of carfilzomib i.v. push at doses of 1.2, 2.4, 4, 6, 8.4, 11, 15, and 20 mg/m2 within 14-day cycles. RESULTS: Twenty-nine patients enrolled that were relapsed or refractory after at least two prior therapies. Nonhematologic toxicities included fatigue, nausea, and diarrhea in more than one third of patients-mostly grade 1 or 2 in severity. At 20 mg/m2, grade 3 febrile neutropenia and grade 4 thrombocytopenia were reported, establishing 15 mg/m2 as the maximum tolerated dose. No grade 3 or 4 peripheral neuropathies were reported. Antitumor activity was observed at doses > or =11 mg/m2: one unconfirmed complete response (mantle cell), one partial response (multiple myeloma), and two minimal responses (multiple myeloma and Waldenström's macroglobulinemia). CONCLUSION: This is the first clinical use of carfilzomib that shows tolerability and clinical activity in multiple hematologic malignancies using consecutive-day dosing.