An anti-CD3/anti-CLL-1 bispecific antibody for the treatment of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a major unmet medical need. Most patients have poor long-term survival, and treatment has not significantly changed in 40 years. Recently, bispecific antibodies that redirect the cytotoxic activity of effector T cells by binding to CD3, the signaling component of the T-cell receptor, and a tumor target have shown clinical activity. Notably, blinatumomab is approved to treat relapsed/refractory acute lymphoid leukemia. Here we describe the design, discovery, pharmacologic activity, pharmacokinetics, and safety of a CD3 T cell-dependent bispecific (TDB) full-length human IgG1 therapeutic antibody targeting CLL-1 that could potentially be used in humans to treat AML. CLL-1 is prevalent in AML and, unlike other targets such as CD33 and CD123, is not expressed on hematopoietic stem cells providing potential hematopoietic recovery. We selected a high-affinity monkey cross-reactive anti-CLL-1 arm and tested several anti-CD3 arms that varied in affinity, and determined that the high-affinity CD3 arms were up to 100-fold more potent in vitro. However, in mouse models, the efficacy differences were less pronounced, probably because of prolonged exposure to TDB found with lower-affinity CD3 TDBs. In monkeys, assessment of safety and target cell depletion by the high- and low-affinity TDBs revealed that only the low-affinity CD3/CLL1 TDB was well tolerated and able to deplete target cells. Our data suggest that an appropriately engineered CLL-1 TDB could be effective in the treatment of AML.

Safety and activity of the anti-CD79B antibody-drug conjugate polatuzumab vedotin in relapsed or refractory B-cell non-Hodgkin lymphoma and chronic lymphocytic leukaemia: a phase 1 study.

BACKGROUND: Patients with relapsed or refractory B-cell non-Hodgkin lymphoma (NHL) have an unfavourable prognosis with few treatment options. Polatuzumab vedotin is an antibody-drug conjugate containing an anti-CD79B monoclonal antibody conjugated to the microtubule-disrupting agent monomethyl auristatin E. We aimed to assess the safety and clinical activity of polatuzumab vedotin in relapsed or refractory B-cell NHL and chronic lymphocytic leukaemia (CLL). METHODS: In this phase 1, multicentre, open-label study, we enrolled patients with documented NHL or CLL expected to express CD79B (confirmation of CD79B expression was not required) and for whom no suitable therapy of curative intent or higher priority existed from 13 centres. The primary endpoints of the study were to assess safety and tolerability, determine the maximum tolerated dose, and identify the recommended phase 2 dose of polatuzumab vedotin as a single agent and in combination with rituximab. A 3 + 3 dose-escalation design was used in which we treated patients with polatuzumab vedotin (0·1-2·4 mg/kg every 21 days) in separate dose-escalation cohorts for NHL and CLL. After determination of the recommended phase 2 dose, we enrolled patients with relapsed or refractory diffuse large B-cell lymphoma and relapsed or refractory indolent NHL into indication-specific cohorts. We also enrolled patients with relapsed or refractory NHL into an additional cohort to assess the feasibility of the combination of polatuzumab vedotin and rituximab 375 mg/m(2). Patients who received any dose of polatuzumab vedotin were available for safety analyses. This study is registered with ClinicalTrials.gov, number NCT01290549. FINDINGS: Between March 21, 2011, and Nov 30, 2012, we enrolled 95 patients (34 to the NHL dose-escalation cohort, 18 to the CLL dose-escalation cohort, 34 with NHL to the expansion cohort at the recommended phase 2 dose, and nine with NHL to the rituximab combination cohort; no expansion cohort of CLL was started due to lack of activity in the dose-escalation cohort). The recommended phase 2 dose in NHL was 2·4 mg/kg as a single agent and in combination with rituximab; the maximum tolerated dose in CLL was 1·0 mg/kg as a result of dose-limiting toxic effects reported in two of five patients given 1·8 mg/kg. Grade 3-4 adverse events were reported in 26 (58%) of 45 patients with NHL treated at the single-agent recommended phase 2 dose, and the most common grade 3-4 adverse events were neutropenia (18 [40%] of 45), anaemia (five [11%]), and peripheral sensory neuropathy (four [9%]). Serious adverse events were reported in 17 (38%) of 45 patients, and included diarrhoea (two patients), lung infection (two patients), disease progression (two patients), and lung disorder (two patients). Seven (77%) of nine patients in the rituximab combination cohort had a grade 3-4 adverse event, with neutropenia (five [56%]), anaemia (two [22%]), and febrile neutropenia (two [22%]) reported in more than one patient. 11 (12%) of 95 patients died during the study: eight with relapsed or refractory diffuse large B-cell lymphoma (due to progressive disease in four patients, infections in three patients [two treatment related], and treatment-related worsening ascites in one patient) and three with relapsed or refractory CLL (due to progressive disease, pulmonary infection, and pneumonia; none thought to be treatment-related). At the recommended phase 2 dose, objective responses were noted in 23 of 42 activity-evaluable patients with NHL given single-agent polatuzumab vedotin (14 of 25 with diffuse large B-cell lymphoma, seven of 15 with indolent NHL, and two with mantle-cell lymphoma) and seven of nine patients treated with polatuzumab vedotin combined with rituximab. No objective responses were observed in patients with CLL. INTERPRETATION: Polatuzumab vedotin has an acceptable safety and tolerability profile in patients with NHL but not in those with CLL. Its clinical activity should be further assessed in NHL. FUNDING: Genentech.

Antibody-drug conjugates for the treatment of B-cell non-Hodgkin's lymphoma and leukemia.

Antibody-drug conjugates (ADCs) are a broad class of molecules comprising of a potent cytotoxic agent conjugated with a monoclonal antibody using a chemically stable linker. By selecting a monoclonal antibody directed against a tumor-specific or tumor-associated antigen, ADCs allow the targeted delivery of highly potent cytotoxic agents that result in unacceptable toxicity when administered as free agents. ADCs are currently being developed for the treatment of a wide variety of tumors. In this review, the current clinical and preclinical status of ADCs for the treatment of B-cell non-Hodgkin's lymphoma and B-cell leukemia will be discussed. ADCs have the potential to alter treatment paradigms for these diseases by providing both increased efficacy and improved safety and tolerability over current chemotherapy-based regimens.

Exogenous insulin-like growth factor 1 enhances thymopoiesis predominantly through thymic epithelial cell expansion.

Insulin-like growth factor 1 (IGF-1) enhances thymopoiesis but given the broad distribution of IGF-1 receptors (IGF-1Rs), its mechanism of action has remained unclear. To identify points of thymic regulation by IGF-1, we examined its effects on T-cell precursors, thymocytes, and thymic epithelial cells (TECs) in normal and genetically altered mice. In thymus-intact but not thymectomized mice, IGF-1 administration increased peripheral naive and recent thymic emigrant (RTE) populations, demonstrating its effect on T-cell production, not peripheral expansion. IGF-1 administration increased bone marrow LSK (lineage(-), Sca-1(+), c-kit(+)) precursor proliferation and peripheral LSK populations, increased thymocyte populations in a sequential wave of expansion, and proportionately expanded TEC subpopulations and enhanced their chemokine expression. To separate IGF-1's effects on thymocytes and TECs, we generated mice lacking IGF-1R on thymocytes and T cells. Thymocyte and RTE numbers were decreased in these mice, but IGF-1 treatment produced comparable thymocyte numbers to similarly treated wild-type mice. We additionally separated thymic- from LSK-specific effects by demonstrating that IGF-1 increased thymocyte numbers despite impaired early thymic progenitor (ETP) importation in PSGL-1KO mice. These results indicate the critical point thymic function regulation by IGF-1 involves TEC expansion regulating thymocyte precursor entry and facilitating thymocyte development.

CCL25 increases thymopoiesis after androgen withdrawal.

Although studies have demonstrated that androgen withdrawal increases thymic size, molecular mechanisms underlying this expansion remain largely unknown. We show that decreased androgen signaling leads to enhanced immigration of bone marrow T-cell precursors, as manifested by both an early increase of early thymic progenitors (ETP) and improved uptake of adoptively transferred quantified precursors into congenic castrated hosts. We provide evidence that the ETP niche is enhanced after androgen withdrawal by proliferation of UEA(+) thymic epithelial cells (TEC) and increased TEC production of CCL25, a ligand critical for ETP entry. Moreover, the greatest increase in CCL25 production is by UEA(+) TEC, linking function of this subset with the increase in ETP immigration. Furthermore, blockade of CCL25 abrogated the effects of castration by impairing ETP entry, retarding immature thymocyte development, limiting increase of thymic size, and impairing increase of thymopoiesis. Taken together, these findings describe a cohesive mechanism underlying increased thymic productivity after androgen withdrawal.

Mitigating the risk of cytokine release syndrome in a Phase I trial of CD20/CD3 bispecific antibody mosunetuzumab in NHL: impact of translational system modeling.

Mosunetuzumab, a T-cell dependent bispecific antibody that binds CD3 and CD20 to drive T-cell mediated B-cell killing, is currently being tested in non-Hodgkin lymphoma. However, potent immune stimulation with T-cell directed therapies poses the risk of cytokine release syndrome, potentially limiting dose and utility. To understand mechanisms behind safety and efficacy and explore safety mitigation strategies, we developed a novel mechanistic model of immune and antitumor responses to the T-cell bispecifics (mosunetuzumab and blinatumomab), including the dynamics of B- and T-lymphocytes in circulation, lymphoid tissues, and tumor. The model was developed and validated using mosunetuzumab nonclinical and blinatumomab clinical data. Simulations delineated mechanisms contributing to observed cell and cytokine (IL6) dynamics and predicted that initial step-fractionated dosing limits systemic T-cell activation and cytokine release without compromising tumor response. These results supported a change to a step-fractionated treatment schedule of mosunetuzumab in the ongoing Phase I clinical trial, enabling safer administration of higher doses.

Polatuzumab vedotin or pinatuzumab vedotin plus rituximab in patients with relapsed or refractory non-Hodgkin lymphoma: final results from a phase 2 randomised study (ROMULUS).

BACKGROUND: Antibody-drug conjugates (ADCs) polatuzumab vedotin (pola) and pinatuzumab vedotin (pina) showed clinical activity and tolerability in phase 1 trials. The aim of this multicentre, open-label, phase 2 study was to compare rituximab plus pola (R-pola) or pina (R-pina) in patients with relapsed or refractory diffuse large B-cell lymphoma and follicular lymphoma. METHODS: In this phase 2 randomised study at 39 investigational sites in six countries, patients were randomly assigned (1:1), by use of a dynamic hierarchical randomisation scheme, to receive R-pola or R-pina (375 mg/m2 rituximab plus 2·4 mg/kg ADCs) every 21 days until disease progression or unacceptable toxicity up to 1 year. Treatment allocations were not masked to the investigator, patients or sponsor after the patients were enrolled and randomly assigned. The primary objectives were safety and tolerability, and antitumour response. The study is registered with ClinicalTrials.gov, number NCT01691898, and is closed to accrual. FINDINGS: 81 patients with diffuse large B-cell lymphoma and 42 with follicular lymphoma were recruited between Sept 27, 2012, and Oct 10, 2013, and were assigned to treatment. 81 patients with diffuse large B-cell lymphoma and 41 patients with follicular lymphoma were eligible for analysis. Of the 42 patients with diffuse large B-cell lymphoma who received R-pina, 25 (60%, 95% CI 43-74) achieved an objective response and 11 (26%, 95% CI 14-42) achieved a complete response. Of the 39 patients in this cohort who received R-pola, 21 (54%, 95% CI 37-70) achieved an objective response, and eight (21%, 95% CI 9-36) achieved a complete response. Of the 21 patients in the follicular lymphoma cohort who received R-pina, 13 (62%, 95% CI 38-82) achieved an objective response, and one (5%, 95% CI 0·1-24) achieved a complete response. Of the 20 patients in this cohort who received R-pola, 14 (70%, 95% CI 46-88) achieved an objective response, and nine (45%, 95% CI 23-68) achieved a complete response. In the diffuse large B-cell lymphoma cohort, grade 3-5 adverse events occurred in 33 (79%) of 42 patients receiving R-pina (most common were neutropenia [29%] and hyperglycaemia [10%]; nine [21%] grade 5 adverse events, five of which were infection-related), and in 30 (77%) of 39 patients receiving R-pola (most common were neutropenia [23%], anaemia [8%] and diarrhoea [8%]; no grade 5 adverse events). In the follicular lymphoma cohort, grade 3-5 adverse events occurred in 13 (62%) of 21 patients receiving R-pina (most common were neutropenia [29%] and hyperglycaemia [14%]; no grade 5 adverse events) and in ten (50%) of 20 patients receiving R-pola (most common were neutropenia [15%] and diarrhoea [10%]; one grade 5 adverse event). INTERPRETATION: R-pina and R-pola are potential treatment options in patients with relapsed or refractory diffuse large B-cell lymphoma and follicular lymphoma. Pola was selected by the study funder for further development in non-Hodgkin lymphoma, partly because of longer durations of response than pina, and an overall benefit-risk favouring R-pola. FUNDING: F Hoffmann-La Roche.

Murine models of chronic graft-versus-host disease: insights and unresolved issues.

Chronic graft-versus-host-disease (cGVHD) is a major barrier to successful allogeneic hematopoietic stem cell transplantation (allo-HSCT), with highly variable clinical presentations. The pathophysiology of cGVHD remains relatively poorly understood. The utilization of murine models to study cGVHD encompasses experimental challenges distinct from those that have been successfully used to study acute GVHD (aGVHD). Nevertheless, despite these challenges, murine models of cGVHD have contributed to the understanding of cGVHD, and highlight its mechanistic complexity. In this article, insights into the pathophysiology of cGVHD obtained from murine studies are summarized in the context of their relevancy to clinical cGVHD. Despite experimental limitations, current and future models of murine cGVHD will continue to provide insights into the understanding of clinical cGVHD and provide information for new therapeutic interventions.

Assessment of Correlation Between Early and Late Efficacy Endpoints to Identify Potential Surrogacy Relationships in Non-Hodgkin Lymphoma: a Literature-Based Meta-analysis of 108 Phase II and Phase III Studies.

Correlations between early and late efficacy endpoints were assessed to identify potential surrogate endpoints for overall survival (OS) or progression-free survival (PFS) with clinical trial-level data in three non-Hodgkin lymphoma (NHL) subtypes: diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), and mantle cell lymphoma (MCL). One hundred and eight phase II-III trials (129 trial arms) in DLBCL, FL, and MCL were identified and included in the database. Correlations between efficacy endpoints were analyzed using weighted linear regression and Pearson's coefficient of determination (R 2). In newly diagnosed DLBCL, 6-month PFS was strongly correlated with 2-year OS (R 2 = 0.81, 95% confidence interval [CI] 0.51-0.96). Six-month PFS was strongly correlated with 3-year PFS (R 2 = 0.89, 95% CI 0.62-0.96) in FL and was moderately correlated with 2-year OS (R 2 = 0.69, 95% CI 0.40-0.91) in MCL trials. Linear regression determined that a 10% increase in 6-month PFS would yield a 13% ± 1.2% increase in 2-year OS in DLBCL, a 23% ± 1.1% increase in 3-year PFS in FL, or a 6.7% ± 1.0% increase in 2-year OS in MCL. Both 6-month PFS and complete response (CR) rate were moderately correlated with median PFS in FL trials with R 2 = 0.66 (95% CI 0.52-0.98) and R 2 = 0.69 (95% CI 0.22-0.89), respectively. Six-month PFS is a potential surrogate endpoint for 2-year OS in newly diagnosed DLBCL and MCL and for 3-year PFS in FL. Both 6-month PFS and CR rate are potential surrogate endpoints for median PFS in FL patients. Confirmation and validation of these correlations may facilitate early interpretation of NHL trials.

Phase I Study of the Anti-CD22 Antibody-Drug Conjugate Pinatuzumab Vedotin with/without Rituximab in Patients with Relapsed/Refractory B-cell Non-Hodgkin Lymphoma.

Purpose: Pinatuzumab vedotin is an antibody-drug conjugate with the potent antimicrotubule agent monomethyl auristatin E (MMAE) conjugated to an anti-CD22 antibody via a protease-cleavable linker. This phase I study determined its recommended phase II dose (RP2D) and evaluated its safety, tolerability, and antitumor activity alone and with rituximab in relapsed/refractory (r/r) non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL).Experimental Design: Patients received escalating doses of pinatuzumab vedotin every 21 days. Clinical activity at the RP2D alone or with rituximab was evaluated in r/r diffuse large B-cell lymphoma (DLBCL) and r/r indolent NHL (iNHL) patients.Results: Seventy-five patients received single-agent pinatuzumab vedotin. The RP2D was 2.4 mg/kg, based on dose-limiting toxicities (DLT) of grade 4 neutropenia >7 days in 1 of 3 patients and grade 4 neutropenia <7 days in 2 of 3 patients treated at 3.2 mg/kg (maximum assessed dose). No DLTs occurred at 2.4 mg/kg. At the RP2D, neutropenia was the most common grade ≥3 adverse event. Peripheral neuropathy-related grade ≥2 adverse events most frequently resulted in treatment discontinuation. Rituximab cotreatment did not impact safety, tolerability, or pharmacokinetics of pinatuzumab vedotin. Unconjugated MMAE exposure was much lower than antibody-conjugated MMAE exposure, without accumulation with repeat dosing. At the RP2D, objective responses were observed in DLBCL (9/25) and iNHL (7/14) patients; 2 of 8 patients treated with pinatuzumab vedotin (RP2D) and rituximab had complete responses. CLL patients showed no objective responses.Conclusions: The RP2D of pinatuzumab vedotin alone and with rituximab was 2.4 mg/kg, which was well tolerated, with encouraging clinical activity in r/r NHL. Clin Cancer Res; 23(5); 1167-76. ©2016 AACR.