Selective inhibition of FLT3 by gilteritinib in relapsed or refractory acute myeloid leukaemia: a multicentre, first-in-human, open-label, phase 1-2 study

Background

Fms-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) mutations are common in acute myeloid leukemia (AML) and are associated with rapid relapse and short survival. In relapsed/refractory (R/R) AML, the clinical benefit of FLT3 inhibitors has been limited by rapid generation of resistance mutations, especially FLT3-D835. Gilteritinib is a potent, highly selective oral FLT3/AXL inhibitor with preclinical activity against FLT3-ITD and FLT3-D835 mutations. The aim of this Phase 1/2 study was to assess the safety, tolerability, and pharmacokinetic (PK) effects of gilteritinib in FLT3 mutation-positive (FLT3^mut+) R/R AML.

Methods

This ongoing pharmacodynamic-driven Phase 1/2 trial (NCT02014558) enrolled subjects from October 2013 to August 2015 who were aged ≥18 years and were either refractory to induction therapy or had relapsed after achieving remission with prior therapy. Subjects were enrolled in one of seven dose-escalation or dose-expansion cohorts that were assigned to receive once-daily doses of oral gilteritinib (20, 40, 80, 120, 200, 300, or 450 mg). Cohort expansion was based on safety/tolerability, FLT3 inhibition in correlative assays, and antileukemic activity; the 120 and 200 mg dose cohorts were further expanded to include FLT3^mut+ patients only. Safety and tolerability, and PK effects were the primary endpoints; antileukemic response was the main secondary endpoint. Safety and tolerability were assessed by monitoring dose-limiting toxicities and treatment-emergent adverse events, and safety assessments (eg, clinical laboratory evaluations, electrocardiograms) in the Safety Analysis Set.

Findings

A total of 252 adults with R/R AML, including 58 with wild-type FLT3 and 194 with FLT3 mutations (FLT3-ITD, n=162; FLT3-D835, n=16; FLT3-ITD and -D835, n=13; other, n=3), received oral gilteritinib (20–450 mg) once daily in one of seven dose-escalation (n=23) or dose-expansion (n=229) cohorts. Gilteritinib was well tolerated in this heavily pretreated population; Grade 3 diarrhea and hepatic transaminase elevation limited dosing above 300 mg/d. The most common Grade 3/4 adverse events were febrile neutropenia (39%; n=97/252), anemia (24%; n=61/252), thromobocytopenia (13%; n=33/252), sepsis (11%; n=28/252), and pneumonia (11%; n=27/252). Serious adverse events in ≥5% of patients were febrile neutropenia (31%; n=78/252), progressive disease (17%; n=43/252), sepsis (14%; n=36/252), pneumonia (11%; n=27/252), and acute renal failure (10%; n=25/252), pyrexia (8%; n=21/252), bacteremia (6%; n=14/252), and respiratory failure (6%; n=14/252). Gilteritinib demonstrated consistent, potent inhibition of FLT3 phosphorylation at doses ≥80 mg/d in correlative assays. While responses were observed across all dose levels regardless of FLT3 mutation status (overall response rate [ORR]=40%), response rate was improved in FLT3^mut+ patients at doses ≥80 mg/d (ORR=52%). Among patients with FLT3-ITD, the additional presence of FLT3-D835 did not alter response rate; patients with only FLT3-D835 responded less frequently.

Interpretation

Gilteritinib had a favorable safety profile and generated potent FLT3 inhibition leading to high rates of antileukemic responses in patients with FLT3^mut+ R/R AML. These findings confirm that FLT3 is a high-value target in R/R AML and that long-term success of therapeutic FLT3 inhibition in AML is optimized by agents with potent, selective, and sustained activity against FLT3-ITD mutations and FLT3 tyrosine kinase domain mutations.

Funding

This study was funded by Astellas Pharma, Inc., by a National Cancer Institute Leukemia Specialized Program of Research Excellence grant (CA100632) awarded to Drs Mark Levis and Jorge Cortes, and by Associazione Italiana Ricerca sul Cancro awarded to Professor Giovanni Martinelli.

Luspatercept in Patients with Lower-Risk Myelodysplastic Syndromes

BACKGROUND

Patients with anemia and lower-risk myelodysplastic syndromes in whom erythropoiesis-stimulating agent therapy is not effective generally become dependent on red-cell transfusions. Luspatercept, a recombinant fusion protein that binds transforming growth factor β superfamily ligands to reduce SMAD2 and SMAD3 signaling, showed promising results in a phase 2 study.

METHODS

In a double-blind, placebo-controlled, phase 3 trial, we randomly assigned patients with very-low-risk, low-risk, or intermediate-risk myelodysplastic syndromes (defined according to the Revised International Prognostic Scoring System) with ring sideroblasts who had been receiving regular red-cell transfusions to receive either luspatercept (at a dose of 1.0 up to 1.75 mg per kilogram of body weight) or placebo, administered subcutaneously every 3 weeks. The primary end point was transfusion independence for 8 weeks or longer during weeks 1 through 24, and the key secondary end point was transfusion independence for 12 weeks or longer, assessed during both weeks 1 through 24 and weeks 1 through 48.

RESULTS

Of the 229 patients enrolled, 153 were randomly assigned to receive luspatercept and 76 to receive placebo; the baseline characteristics of the patients were balanced. Transfusion independence for 8 weeks or longer was observed in 38% of the patients in the luspatercept group, as compared with 13% of those in the placebo group (P<0.001). A higher percentage of patients in the luspatercept group than in the placebo group met the key secondary end point (28% vs. 8% for weeks 1 through 24, and 33% vs. 12% for weeks 1 through 48; P<0.001 for both comparisons). The most common luspatercept-associated adverse events (of any grade) included fatigue, diarrhea, asthenia, nausea, and dizziness. The incidence of adverse events decreased over time.

CONCLUSIONS

Luspatercept reduced the severity of anemia in patients with lower-risk myelodysplastic syndromes with ring sideroblasts who had been receiving regular red-cell transfusions and who had disease that was refractory to or unlikely to respond to erythropoiesis-stimulating agents or who had discontinued such agents owing to an adverse event. (Funded by Celgene and Acceleron Pharma; MEDALIST ClinicalTrials.gov number, NCT02631070; EudraCT number, 2015-003454-41.).

Radioimmunotherapy with alpha-emitting nuclides

This review discusses the application of alpha particle-emitting radionuclides in targeted radioimmunotherapy. It will outline the production and chemistry of astatine-211, bismuth-212, lead-212, actinium-225, bismuth-213, fermium-255, radium-223 and terbium-149, which at present are the most promising alpha-emitting isotopes available for human clinical use. The selective cytotoxicity offered by alpha particle-emitting radioimmunoconstructs is due to the high linear energy transfer and short particle path length of these radionuclides. Based upon the pharmacokinetics of alpha particle-emitting radioimmunoconstructs, both stochastic and conventional dosimetric methodology is discussed, as is the preclinical and initial clinical use of these radionuclides conjugated to monoclonal antibodies for the treatment of human neoplasia.

Refractory Aspergillus pneumonia in patients with acute leukemia: successful therapy with combination caspofungin and liposomal amphotericin

BACKGROUND

Pulmonary aspergillosis and other invasive fungal infections (IFIs) commonly complicate the management of patients with acute leukemia. Standard amphotericin-based therapies may be ineffective for many patients and the available salvage agents (itraconazole and caspofungin) are reported to possess only moderate activity against resistant infections. Laboratory evidence suggests a synergistic interaction between amphotericin and caspofungin. The authors treated a group of patients with amphotericin-refractory IFIs with the combination of caspofungin and amphotericin (or liposomal amphotericin).

METHODS

A retrospective evaluation of patients with amphotericin-resistant IFIs was conducted. Diagnosis was based on clinical, radiographic, and when available, microbiologic data. Response to combination antifungal therapy was graded as either favorable or unfavorable. Favorable responses included improvement of both clinical and radiographic signs of fungal pneumonia. All other responses were graded as unfavorable.

RESULTS

Thirty patients were included in this analysis. Twenty-six patients had acute leukemia. Based on recently published criteria, the IFIs were classified as proven in 6 patients, probable in 4 patients, and possible in 20 patients. The median duration and dose of amphotericin monotherapy were 12 days (range, 4-65 days) and 7.8 mg/kg (range, 4.2-66.1 mg/kg), respectively. The median duration of combination therapy was 24 days (range, 3-74 days). Eighteen patients (60%) experienced a favorable antifungal response. Twenty patients with acute leukemia received combination therapy for fungal pneumonias arising during intensive chemotherapy treatments. Favorable responses were observed in 15 of these patients (75%), and antifungal response did not depend on the response of the underlying leukemia. Survival to hospital discharge was significantly better (P < 0.001) in patients having a favorable response. Mild to moderate nephrotoxicity was noted in 50% of patients, necessitating the substitution of liposomal amphotericin. Mild elevation of alkaline phosphatase levels occurred in 30% of patients. Caspofungin was temporarily withheld from one patient who developed moderate but reversible biochemical hepatotoxicity.

CONCLUSIONS

The antifungal combination of caspofungin and amphotericin can be administered safely to high-risk patients with hematologic malignancies. Although an absolute assessment of efficacy is limited by the design of this study, encouraging outcomes were noted for many patients. The authors plan to evaluate this regimen further in a randomized clinical trial.

Sequential cytarabine and alpha-particle immunotherapy with bismuth-213-lintuzumab (HuM195) for acute myeloid leukemia

PURPOSE

Lintuzumab (HuM195), a humanized anti-CD33 antibody, targets myeloid leukemia cells and has modest single-agent activity against acute myeloid leukemia (AML). To increase the potency of the antibody without the nonspecific cytotoxicity associated with β-emitters, the α-particle-emitting radionuclide bismuth-213 ((213)Bi) was conjugated to lintuzumab. This phase I/II trial was conducted to determine the maximum tolerated dose (MTD) and antileukemic effects of (213)Bi-lintuzumab, the first targeted α-emitter, after partially cytoreductive chemotherapy.

EXPERIMENTAL DESIGN

Thirty-one patients with newly diagnosed (n = 13) or relapsed/refractory (n = 18) AML (median age, 67 years; range, 37-80) were treated with cytarabine (200 mg/m(2)/d) for 5 days followed by (213)Bi-lintuzumab (18.5-46.25 MBq/kg).

RESULTS

The MTD of (213)Bi-lintuzumab was 37 MB/kg; myelosuppression lasting >35 days was dose limiting. Extramedullary toxicities were primarily limited to grade ≤2 events, including infusion-related reactions. Transient grade 3/4 liver function abnormalities were seen in five patients (16%). Treatment-related deaths occurred in 2 of 21 (10%) patients who received the MTD. Significant reductions in marrow blasts were seen at all dose levels. The median response duration was 6 months (range, 2-12). Biodistribution and pharmacokinetic studies suggested that saturation of available CD33 sites by (213)Bi-lintuzumab was achieved after partial cytoreduction with cytarabine.

CONCLUSIONS

Sequential administration of cytarabine and (213)Bi-lintuzumab is tolerable and can produce remissions in patients with AML.

Pentostatin, cyclophosphamide, and rituximab is an active, well-tolerated regimen for patients with previously treated chronic lymphocytic leukemia

PURPOSE

Purine analogs and alkylators are important agents for treating chronic lymphocytic leukemia (CLL). Early studies combining fludarabine and chlorambucil were abandoned owing to increased toxicity from overlapping myelosuppression and immunosuppression. Of the purine analogs active in CLL, pentostatin appears to be the least myelosuppressive. We previously reported that pentostatin and cyclophosphamide (PC) is active and well-tolerated in patients with relapsed or refractory CLL. Subsequently, we added rituximab, and now report on this three-drug combination.

PATIENTS AND METHODS

We treated 46 patients with either previously treated CLL (32 patients) or other low-grade B-cell neoplasms (14 patients). Patients received pentostatin 4 mg/m2, cyclophosphamide 600 mg/m2, and rituximab 375 mg/m2 (PCR). All drugs were administered on the same day (rituximab omitted from cycle 1), and patients received six cycles at 3-week intervals. Filgrastim, sulfamethoxazole/trimethoprim, and acyclovir were administered prophylactically.

RESULTS

The median age was 62 years (range, 30 to 80 years). The median number of prior regimens was two (range, one to seven). For CLL patients, there were 24 responses (75%), including eight complete responses (25%). In fludarabine-refractory patients, 75% responded. Toxicity was acceptable, with grade 3/4 infections (including fever of unknown origin) in 28%. The regimen was well tolerated, with 72% of patients receiving the planned treatment at full dose.

CONCLUSION

PCR is safe and effective in previously treated patients with CLL. In comparison with our prior two-drug regimen, we find that rituximab did not seem to add significantly to the toxicity, but did appear to confer a survival advantage. Based on these results, we are currently studying PCR as initial therapy for patients with CLL.

Phase 2 trial of a multivalent WT1 peptide vaccine (galinpepimut-S) in acute myeloid leukemia

A National Cancer Institute consensus study on prioritization of cancer antigens ranked the Wilms tumor 1 (WT1) protein as the top immunotherapy target in cancer. We previously reported a pilot study of a multivalent WT1 peptide vaccine (galinpepimut-S) in acute myeloid leukemia (AML) patients. We have now conducted a phase 2 study investigating this vaccine in adults with AML in first complete remission (CR1). Patients received 6 vaccinations administered over 10 weeks with the potential to receive 6 additional monthly doses if they remained in CR1. Immune responses (IRs) were evaluated after the 6th and 12th vaccinations by CD4+ T-cell proliferation, CD8+ T-cell interferon-γ secretion (enzyme-linked immunospot), or the CD8-relevant WT1 peptide major histocompatibility complex tetramer assay (HLA-A*02 patients only). Twenty-two patients (7 males; median age, 64 years) were treated. Fourteen patients (64%) completed ≥6 vaccinations, and 9 (41%) received all 12 vaccine doses. Fifteen patients (68%) relapsed, and 10 (46%) died. The vaccine was well tolerated, with the most common toxicities being grade 1/2 injection site reactions (46%), fatigue (32%), and skin induration (32%). Median disease-free survival from CR1 was 16.9 months, whereas the overall survival from diagnosis has not yet been reached but is estimated to be ≥67.6 months. Nine of 14 tested patients (64%) had an IR in ≥1 assay (CD4 or CD8). These results indicated that the WT1 vaccine was well tolerated, stimulated a specific IR, and was associated with survival in excess of 5 years in this cohort of patients. This trial was registered at www.clinicaltrials.gov as #NCT01266083.

Sotatercept with long-term extension for the treatment of anaemia in patients with lower-risk myelodysplastic syndromes: a phase 2, dose-ranging trial

BACKGROUND

Myelodysplastic syndromes are characterised by ineffective erythropoiesis leading to anaemia. Sotatercept (ACE-011) is a novel activin receptor type IIA fusion protein that acts as a ligand trap to neutralise negative regulators of late-stage erythropoiesis. The aim of the study was to establish a safe and effective dose of sotatercept for the treatment of anaemia in patients with lower-risk myelodysplastic syndromes.

METHODS

This open-label, multicentre, dose-ranging, phase 2 trial took place at 11 treatment centres in the USA and France. Eligible patients were aged 18 years or older, had International Prognostic Scoring System-defined low-risk or intermediate-1-risk myelodysplastic syndromes, had anaemia requiring red blood cell (RBC) transfusions, and were ineligible for, or refractory to, erythropoiesis-stimulating agents (ESAs). Patients were not eligible if they had chromosome 5q deletion myelodysplastic syndromes without documented failure of lenalidomide. Patients were randomly assigned to receive either 0·1 or 0·3 mg/kg sotatercept subcutaneously, using a permuted-block method with stratification for serum erythropoietin concentration and transfusion burden. Patients were assigned to 0·5, 1·0, and 2·0 mg/kg groups in a non-randomised fashion. The primary efficacy endpoint was the proportion of patients who achieved haematological improvement-erythroid (HI-E), according to International Working Group 2006 criteria. Efficacy and safety analyses were done in the intention-to-treat population. This trial is registered at ClinicalTrials.gov, number NCT01736683 and at EU Clinical Trials Register, number 2012-002601-22, and is ongoing.

FINDINGS

Between Dec 5, 2012, and July 22, 2015, 74 patients were enrolled into the study (seven to receive 0·1 mg/kg sotatercept, six to 0·3 mg/kg, 21 to 0·5 mg/kg, 35 to 1·0 mg/kg, and five to 2·0 mg/kg). 36 (49%; 95% CI 38-60) of 74 patients achieved HI-E; 29 (47%; 95% CI 35-59) of 62 patients with a high transfusion burden achieved HI-E (RBC-transfusion reduction from baseline of 4 or more units for at least 56 days), and seven (58%; 95% CI 32-81) of 12 patients with a low transfusion burden achieved HI-E (haemoglobin increase of 1·5 g/dL or more sustained for at least 56 days in the absence of transfusions). The most commonly reported adverse events were fatigue in 19 (26%) of 74 patients and peripheral oedema in 18 (24%) of 74 patients. Grade 3-4 treatment-emergent adverse events (TEAEs) were reported in 25 (34%) of 74 patients; four (5%) patients had grade 3-4 TEAEs that were considered to be treatment related. The most common grade 3-4 TEAEs were lipase increase and anaemia, which each occurred in three (4%) of 74 patients. 17 (23%) of 74 patients had at least one serious TEAE, and one patient died from a treatment-emergent subdural haematoma due to a fall.

INTERPRETATION

Sotatercept, a novel activin-receptor fusion protein, was well tolerated and effective for the treatment of anaemia in patients with lower-risk myelodysplastic syndromes in whom previous ESA treatment had failed. Treatment with sotatercept could be beneficial for these patients who have few available treatment options.

FUNDING

Celgene Corporation.

Pentostatin and cyclophosphamide: an effective new regimen in previously treated patients with chronic lymphocytic leukemia

PURPOSE

Purine analogs and alkylators are important agents in the treatment of chronic lymphocytic leukemia (CLL). Previously, combinations of fludarabine and chlorambucil were abandoned because of increased toxicity from overlapping myelosuppression and immunosuppression. Of the purine analogs active in CLL, pentostatin may be least myelosuppressive. We hypothesized that combining pentostatin with cyclophosphamide would have less myelotoxicity than combinations using other purine analogs.

PATIENTS AND METHODS

We studied 23 patients with previously treated CLL. All patients received pentostatin 4 mg/m(2). Seventeen patients received cyclophosphamide 600 mg/m(2), and six patients received cyclophosphamide 900 mg/m(2). Both drugs were administered on day 1 of each cycle, and cycles were repeated every 3 weeks for six treatments. Filgrastim, sulfamethoxazole/trimethoprim, and acyclovir were administered prophylactically. The median number of prior treatment regimens was three (range, one to five) with 13 patients (57%) refractory to prior fludarabine therapy.

RESULTS

The cyclophosphamide 900 mg/m(2) dose level was associated with moderate to severe nausea, and we chose cyclophosphamide 600 mg/m(2) as the dose for further study. There were 17 responses (74%; 95% confidence interval, 63% to 85%), including four complete responses. The response rate was 77% in fludarabine-refractory patients. Myelosuppression was acceptable with grade 3/4 neutropenia and thrombocytopenia, seen in 35% and 30% of patients, respectively. The relative sparing of thrombopoiesis can be seen in that only one patient (5%) with an initial platelet count of more than 20,000 required platelet transfusions while receiving therapy.

CONCLUSION

Pentostatin 4 mg/m(2) with cyclophosphamide 600 mg/m(2) is safe and effective in previously treated patients with CLL. On the basis of these results, we are currently studying pentostatin, cyclophosphamide, and rituximab (PCR) therapy in patients with CLL.

Randomized phase IIb study of low-dose cytarabine and lintuzumab versus low-dose cytarabine and placebo in older adults with untreated acute myeloid leukemia

Improving outcomes in older adults with acute myeloid leukemia remains a formidable challenge. Lintuzumab (SGN-33; HuM195) is a humanized monoclonal antibody directed against CD33, which is expressed on the majority of myeloblasts in acute myeloid leukemia. The primary objective of this randomized, double-blinded, placebo-controlled trial was to determine whether addition of lintuzumab to low-dose cytarabine would increase overall survival in adults aged 60 years and over with untreated acute myeloid leukemia. Randomization was stratified by age, previous hematologic disorder, and performance status. All patients received cytarabine (20 mg subcutaneously twice daily) on Days 1-10 of each 28-day cycle. Patients received lintuzumab (600 mg) or placebo intravenously once weekly in Cycle 1 and once every other week in Cycles 2-12. A total of 211 patients (107 lintuzumab, 104 placebo) were randomized. Median age was 70 years (range 60-90). Survival was not significantly prolonged with lintuzumab treatment (hazard ratio 0.96; 95% confidence interval (CI) 0.72-1.28; P=0.7585). Median survival was similar between treatment arms (4.7 months lintuzumab vs. 5.1 months placebo) and in the subgroup of patients with high-risk cytogenetics (4.5 months). Infusion-related reactions, predominantly Grades 1-2, occurred more commonly in the lintuzumab arm (51% vs. 7% placebo); no other clinically significant difference in safety was noted. These results confirm that lintuzumab in combination with low-dose cytarabine did not prolong survival and that low-dose cytarabine remains a valid comparator for trials of non-intensive therapies in older patients with acute myeloid leukemia, regardless of cytogenetic profile.

Cytoreduction with iodine-131-anti-CD33 antibodies before bone marrow transplantation for advanced myeloid leukemias

The monoclonal antibodies M195 and HuM195 target CD33, a glycoprotein found on myeloid leukemia cells. When labeled with iodine-131 ((131)I), these antibodies can eliminate large disease burdens and produce prolonged myelosuppression. We studied whether (131)I-labeled M195 and HuM195 could be combined safely with busulfan and cyclophosphamide (BuCy) as conditioning for allogeneic BMT. A total of 31 patients with relapsed/refractory acute myeloloid leukemia (AML) (n=16), accelerated/myeloblastic chronic myeloid leukemia (CML) (n=14), or advanced myelodysplastic syndrome (n=1) received (131)I-M195 or (131)I-HuM195 (122-437 mCi) plus busulfan (16 mg/kg) and cyclophosphamide (90-120 mg/kg) followed by infusion of related-donor bone marrow (27 first BMT; four second BMT). Hyperbilirubinemia was the most common extramedullary toxicity, occurring in 69% of patients during the first 28 days after BMT. Gamma camera imaging showed targeting of the radioisotope to the bone marrow, liver, and spleen, with absorbed radiation doses to the marrow of 272-1470 cGy. The median survival was 4.9 months (range 0.3-90+ months). Three patients with relapsed AML remain in complete remission 59+, 87+, and 90+ months following bone marrow transplantation (BMT). These studies show the feasibility of adding CD33-targeted radioimmunotherapy to a standard BMT preparative regimen; however, randomized trials will be needed to prove a benefit to intensified conditioning with radioimmunotherapy.

Prognostic significance of minimal residual disease detection and PML/RAR-alpha isoform type: long-term follow-up in acute promyelocytic leukemia

The t(15;17) translocation in acute promyelocytic leukemia (APL) yields a PML/RAR-alpha fusion messenger RNA species that can be detected by reverse transcription-polymerase chain reaction (RT-PCR) amplification. Breakpoints within intron 3 of PML produce a short PML/RAR-alpha isoform, whereas breakpoints within intron 6 result in a longer form. Using RT-PCR, serial evaluations were performed on the bone marrow of 82 patients with APL (median follow-up, > 63 months) who received retinoic acid (RA) induction followed by postremission treatment with chemotherapy, RA, and biologic agents. Sixty-four patients attained a clinical complete remission and had at least 2 RT-PCR assays performed after completing therapy. Forty of 47 patients (85%) with newly diagnosed APL who were induced using RA had residual disease detectable by RT-PCR before additional therapy. After 3 cycles of consolidation therapy, residual disease was found in only 4 of 40 evaluable patients (10%). Among newly diagnosed patients who had 2 or more negative RT-PCR assays, only 3 of 41 (7%) had a relapse, whereas all 4 patients (100%) who had 2 or more positive results had a relapse. Among 63 newly diagnosed patients, those who expressed the short isoform appeared to have shorter disease-free and overall survival durations than patients who expressed the long isoform. These data indicate that 2 or more negative RT-PCR assays on bone marrow, performed at least 1 month apart after completing therapy, are strongly associated with long-term remissions. Conversely, a confirmed positive test is highly predictive of relapse.

Magrolimab in Combination With Azacitidine in Patients With Higher-Risk Myelodysplastic Syndromes: Final Results of a Phase Ib Study

PURPOSE

Magrolimab is a monoclonal antibody that blocks cluster of differentiation 47, a don't-eat-me signal overexpressed on cancer cells. Cluster of differentiation 47 blockade by magrolimab promotes macrophage-mediated phagocytosis of tumor cells and is synergistic with azacitidine, which increases expression of eat-me signals. We report final phase Ib data in patients with untreated higher-risk myelodysplastic syndromes (MDS) treated with magrolimab and azacitidine (ClinicalTrials.gov identifier: NCT03248479).

PATIENTS AND METHODS

Patients with previously untreated Revised International Prognostic Scoring System intermediate-/high-/very high-risk MDS received magrolimab intravenously as a priming dose (1 mg/kg) followed by ramp-up to a 30 mg/kg once-weekly or once-every-2-week maintenance dose. Azacitidine 75 mg/m2 was administered intravenously/subcutaneously once daily on days 1-7 of each 28-day cycle. Primary end points were safety/tolerability and complete remission (CR) rate.

RESULTS

Ninety-five patients were treated. Revised International Prognostic Scoring System risk was intermediate/high/very high in 27%, 52%, and 21%, respectively. Fifty-nine (62%) had poor-risk cytogenetics and 25 (26%) had TP53 mutation. The most common treatment-emergent adverse effects included constipation (68%), thrombocytopenia (55%), and anemia (52%). Median hemoglobin change from baseline to first postdose assessment was -0.7 g/dL (range, -3.1 to +2.4). CR rate and overall response rate were 33% and 75%, respectively. Median time to response, duration of CR, duration of overall response, and progression-free survival were 1.9, 11.1, 9.8, and 11.6 months, respectively. Median overall survival (OS) was not reached with 17.1-month follow-up. In TP53-mutant patients, 40% achieved CR with median OS of 16.3 months. Thirty-four patients (36%) had allogeneic stem-cell transplant with 77% 2-year OS.

CONCLUSION

Magrolimab + azacitidine was well tolerated with promising efficacy in patients with untreated higher-risk MDS, including those with TP53 mutations. A phase III trial of magrolimab/placebo + azacitidine is ongoing (ClinicalTrials.gov identifier: NCT04313881 [ENHANCE]).

Sequential therapy with fludarabine, high-dose cyclophosphamide, and rituximab in previously untreated patients with chronic lymphocytic leukemia produces high-quality responses: molecular remissions predict for durable complete responses

PURPOSE

Modern combination strategies are active in chronic lymphocytic leukemia (CLL) but can have significant myelosuppression and immunosuppression that may require dose attenuation for safety. We explored a sequential treatment strategy to allow safe delivery of active agents at full doses. Previously, we studied sequential therapy with fludarabine followed by cyclophosphamide (F-->C). In that study, cyclophosphamide consolidation improved the frequency of complete response (CR) four-fold. Subsequently, rituximab was added to this regimen (F-->C-->R).

PATIENTS AND METHODS

Thirty-six previously untreated CLL patients received therapy with fludarabine 25 mg/m(2) on days 1 through 5 every 4 weeks for six cycles, followed by consolidation with cyclophosphamide 3,000 mg/m(2) administered every 3 weeks for three cycles, followed by consolidation with weekly rituximab 375 mg/m(2) for four cycles. Evaluation for minimal residual disease included flow cytometry and a highly sensitive clonotypic polymerase chain reaction (PCR). The median age was 59 years (range, 37 to 71 years), 61% of patients had high-risk disease, and 58% had unmutated IgV(H) genes.

RESULTS

There were 32 responses (89%), including 22 CRs (61%). Consolidation with cyclophosphamide improved responses in 13 patients (36%); nine patients (25%) further improved their response with rituximab. Twenty patients (56%) achieved flow cytometric CRs, and 12 patients (33%) achieved a molecular CR (PCR negative). Patients achieving molecular CRs had an excellent prognosis with a plateau in the response duration curve, and 90% remain in clinical CR at 5 years. For the entire group, 5-year survival rate is 71% compared with a rate of 48% with our prior F-->C regimen (P = .10).

CONCLUSION

Sequential therapy with F-->C-->R yields improvement in quality of response, with many patients achieving a PCR-negative state.

Olutasidenib (FT-2102) induces durable complete remissions in patients with relapsed or refractory IDH1-mutated AML

Olutasidenib (FT-2102) is a potent, selective, oral, small-molecule inhibitor of mutant isocitrate dehydrogenase 1 (mIDH1). Overall, 153 IDH1 inhibitor-naive patients with mIDH1R132 relapsed/refractory (R/R) acute myeloid leukemia (AML) received olutasidenib monotherapy 150 mg twice daily in the pivotal cohort of this study. The median age of participants was 71 years (range, 32-87 years) and the median number of prior regimens received by patients was 2 (1-7). The rate of complete remission (CR) plus CR with partial hematologic recovery (CRh) was 35%, and the overall response rate was 48%. Response rates were similar in patients who had, and who had not, received prior venetoclax. With 55% of patients censored at the time of data cut-off, the median duration of CR/CRh was 25.9 months. The median duration of overall response was 11.7 months, and the median overall survival was 11.6 months. Of 86 patients who were transfusion dependent at baseline, a 56-day transfusion independence was achieved in 29 (34%), which included patients in all response groups. Grade 3 or 4 treatment-emergent adverse events (≥10%) were febrile neutropenia and anemia (n = 31; 20% each), thrombocytopenia (n = 25; 16%), and neutropenia (n = 20; 13%). Differentiation syndrome adverse events of special interest occurred in 22 (14%) patients, with 14 (9%) grade ≥3 and 1 fatal case reported. Overall, olutasidenib induced durable remissions and transfusion independence with a well-characterized and manageable side effect profile. The observed efficacy represents a therapeutic advance in this molecularly defined, poor-prognostic population of patients with mIDH1 R/R AML. This trial was registered at www.clinicaltrials.gov as #NCT02719574.

Targeted alpha-particle immunotherapy for acute myeloid leukemia

Because alpha-particles have a shorter range and a higher linear energy transfer (LET) compared with beta-particles, targeted alpha-particle immunotherapy offers the potential for more efficient tumor cell killing while sparing surrounding normal cells. To date, clinical studies of alpha-particle immunotherapy for acute myeloid leukemia (AML) have focused on the myeloid cell surface antigen CD33 as a target using the humanized monoclonal antibody lintuzumab. An initial phase I study demonstrated the safety, feasibility, and antileukemic effects of bismuth-213 ((213)Bi)-labeled lintuzumab. In a subsequent study, (213)Bi-lintuzumab produced remissions in some patients with AML after partial cytoreduction with cytarabine, suggesting the utility of targeted alpha-particle therapy for small-volume disease. The widespread use of (213)Bi, however, is limited by its short half-life. Therefore, a second-generation construct containing actinium-225 ((225)Ac), a radiometal that generates four alpha-particle emissions, was developed. A phase I trial demonstrated that (225)Ac-lintuzumab is safe at doses of 3 μCi/kg or less and has antileukemic activity across all dose levels studied. Fractionated-dose (225)Ac-lintuzumab in combination with low-dose cytarabine (LDAC) is now under investigation for the management of older patients with untreated AML in a multicenter trial. Preclinical studies using (213)Bi- and astatine-211 ((211)At)-labeled anti-CD45 antibodies have shown that alpha-particle immunotherapy may be useful as part conditioning before hematopoietic cell transplantation. The use of novel pretargeting strategies may further improve target-to-normal organ dose ratios.

Radioimmunotherapy for acute leukemia

BACKGROUND

The use of monoclonal antibodies to deliver radioactive isotopes directly to tumor cells has become a promising strategy to enhance the antitumor effects of native monoclonal antibodies. In this article, we summarize the role of radioimmunotherapy in the treatment of leukemia.

METHODS

The authors reviewed the published clinical trials of radioimmunotherapy in acute leukemia.

RESULTS

Radioimmunoconjugates that emit beta-particles, such as 131I-anti-CD33, 90Y-anti-CD33, 131I-anti-CD45, and 188Re-anti-CD66c, deliver significant doses of radiation to the bone marrow and may be particularly effective when used as part of a conditioning regimen for hematopoietic stem cell transplantation. Radioimmunoconjugates that emit short-ranged alpha-particles, such as 213Bi-anti-CD33, are better suited for the treatment of low-volume or residual disease.

CONCLUSIONS

Radiolabeled antibodies can be administered safely to patients with advanced leukemias and have significant antileukemic activity. Radiolabeled antibodies can potentially intensify the antileukemic effects of conditioning regimens when used in conjunction with hematopoietic stem cell transplantation. Whether or not radiolabeled antibodies improve the outcome of patients with leukemia remains to be demonstrated by randomized studies.

Prospective international validation of the Quality of Life in Myelodysplasia Scale (QUALMS)

Disease-specific measures of quality of life can improve assessment of disease-related symptoms and psychosocial sequelae. We report on the development and validation of the Quality of Life in Myelodysplasia Scale (QUALMS), a 38-item assessment tool for patients with myelodysplastic syndromes (MDS). In 2014-2015, a multi-center cohort of patients with myelodysplasia completed the QUALMS, as well as the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (QLQ-C30) and the Functional Assessment of Cancer Therapy Anemia Scale (FACT-An); a second administration was undertaken three to six months later. A total of 255 patients from the United States, Canada and Italy participated. Median age was 72 years, 56.1% were men, and the International Prognostic Scoring System distribution was 40.4% low, 42.0% intermediate-1, 13.3% intermediate-2 and 2.3% high. QUALMS scores ranged from 24 to 99 (higher scores are better), with a mean of 67.2 [standard deviation (SD)=15.2]. The measure was internally consistent (α=0.92), and moderately correlated with the multi-item QLQ-C30 scales and the FACT-An (r=-0.65 to 0.79; all P<0.001). Patients with hemoglobin of 8 g/dL or under scored lower than those with hemoglobin over 10 g/dL (61.8 vs 71.1; P<0.001), and transfusion-dependent patients scored lower than transfusion-independent patients (62.4 vs 69.7; P<0.01). Principal components analysis revealed "physical burden", "benefit-finding", and "emotional burden" subscales. There was good overall test-retest reliability among those with stable hemoglobin (r=0.81), and significant changes for patients hospitalized or with infections between administrations (both P<0.01). These data suggest the QUALMS is a valuable tool for assessing MDS-specific quality of life in the modern treatment era.

What happened to anti-CD33 therapy for acute myeloid leukemia?

CD33, a 67-kDa glycoprotein expressed on the majority of myeloid leukemia cells as well as on normal myeloid and monocytic precursors, has been an attractive target for monoclonal antibody (mAb)-based therapy of acute myeloid leukemia (AML). Lintuzumab, an unconjugated, humanized anti-CD33 mAb, has modest single-agent activity against AML but failed to improve patient outcomes in two randomized trials when combined with conventional chemotherapy. Gemtuzumab ozogamicin, an anti-CD33 mAb conjugated to the antitumor antibiotic calicheamicin, improved survival in a subset of AML patients when combined with standard chemotherapy, but safety concerns led to US marketing withdrawal. The activity of these agents confirms that CD33 remains a viable therapeutic target for AML. Strategies to improve the results of mAb-based therapies for AML include antibody engineering to enhance effector function, use of alternative drugs and chemical linkers to develop safer and more effective drug conjugates, and radioimmunotherapeutic approaches.

Complete remissions observed in acute myeloid leukemia following prolonged exposure to lintuzumab: a phase 1 trial

A multi-institutional, phase 1 dose-escalation trial of lintuzumab (humanized anti-CD33 antibody; SGN-33, HuM195) was performed in patients with CD33-positive myeloid malignancies. In this study, higher doses than previously tested and prolonged duration of treatment for responding patients were evaluated. Over the dose range of 1.5-8 mg/kg/week, lintuzumab was well tolerated, and a maximum tolerated dose was not defined. The most common adverse event was transient chills with the initial lintuzumab infusion (39%). Responses were observed in 7 of 17 patients with acute myeloid leukemia: morphologic complete remission (n = 4), partial remission (n = 2), and morphologic leukemia-free state (n = 1). Of 14 patients with myelodysplastic syndrome or myeloproliferative diseases, 1 patient had major hematologic improvement and 9 patients had stable disease. In contrast to aggressive conventional chemotherapy, lintuzumab was administered in an ambulatory clinic setting with acceptable toxicity.

Treatment of Patients with Acute Myeloid Leukemia with the Targeted Alpha-Particle Nano-Generator Actinium-225-Lintuzumab

PURPOSE

The anti-CD33 antibody lintuzumab has modest activity against acute myeloid leukemia (AML). To increase its potency, lintuzumab was conjugated to actinium-225 (225Ac), a radionuclide yielding 4 α-particles. This first-in-human, phase I trial was conducted to determine the safety, pharmacology, and biological activity of 225Ac-lintuzumab.

PATIENTS AND METHODS

Eighteen patients (median age, 64 years; range, 45-80) with relapsed or refractory AML received a single infusion of 225Ac-lintuzumab at activities of 18.5-148 kBq/kg.

RESULTS

The maximum tolerated dose was 111 kBq/kg. Dose-limiting toxicities included myelosuppression lasting &gt; 35 days in one patient receiving 148 kBq/kg and death from sepsis in two patients treated with 111 and 148 kBq/kg. Myelosuppression was the most common toxicity. Significant extramedullary toxicities were limited to transient grade 3 liver function abnormalities. Pharmacokinetics were determined by gamma counting serial whole blood, plasma, and urine samples at energy windows for the 225Ac daughters, francium-221 and bismuth-213. Two-phase elimination kinetics were seen with mean plasma t1/2-α and t1/2-β of 1.9 and 38 hours, respectively. Peripheral blood blasts were eliminated in 10 of 16 evaluable patients (63%) but only at doses of {greater than or equal to} 37 kBq/kg. Bone marrow blasts were reduced in 10 of 15 evaluable patients (67%), including 3 patients with marrow blasts {less than or equal to} 5% and 1 patient with a morphologic leukemia-free state.

CONCLUSIONS

Therapy for AML with the targeted α-particle generator 225Ac-lintuzumab was feasible with an acceptable safety profile. Elimination of circulating blasts or reductions in marrow blasts were observed across all dose levels.

Antibody therapy for residual disease in acute myelogenous leukemia

The elimination of minimal residual disease remains one of the most promising applications of monoclonal antibody (mAb)-based therapies. An early study showed that treatment with iodine-131 (131I)-labeled anti-CD33 mAb M195 had antileukemic effects when given as postremission therapy to patients with acute promyelocytic leukemia (APL) in second remission. This treatment, however, was limited by significant myelosuppression and by the development of neutralizing human antimouse antibodies. Treatment with native HuM195, a humanized version of murine M195, eliminated minimal residual disease detectable by reverse transcription-polymerase chain reaction (RT-PCR) in 50% of patients. Patients with newly diagnosed APL treated with all-trans retinoic acid followed by HuM195 and consolidation chemotherapy had an 87% 3-year disease-free survival. Radioimmunotherapy with short-ranged, high-energy alpha particle-emitting isotopes may increase the potency of native mAbs while avoiding the nonspecific cytotoxicity of beta-emitting constructs. Targeted alpha particle therapy with bismuth-213-HuM195 showed significant antileukemic activity in patients with relapsed or refractory acute myelogenous leukemia. Antibody-drug conjugates, such as gemtuzumab ozogamicin, composed of a humanized anti-CD33 mAb and calicheamicin, have produced complete remissions in patients with relapsed AML and are likely to be active in the postremission setting.

Targeted Alpha-Particle Therapy for Hematologic Malignancies

The short range and high linear energy transfer of α-particles offer the potential for efficient tumor killing while sparing normal bystander cells. Hematologic malignancies are ideally suited to targeted α-particle therapy (TAT) due to easy accessibility of malignant cells in blood, bone marrow, lymph nodes, and spleen as well as their radiosensitivity. Most clinical trials using α-particle therapy for hematologic malignancies have focused on acute myeloid leukemia (AML); however, preclinical studies have shown activity against other diseases such as non-Hodgkin's lymphoma and multiple myeloma. To date, the short-lived radionuclide bismuth-213 (²¹³Bi) and its parent actinium-225 (²²⁵Ac) have been used clinically, but trials with astatinie-211 (²¹¹At) have recently begun, and thorium-227 (²²⁷Th) has shown promising preclinical results. Lintuzumab is a humanized monoclonal antibody that targets the cell surface antigen CD33, which is expressed on the vast majority of AML cells. Initial studies showed that ²¹³Bi-labeled lintuzumab had antileukemic activity and could produce remissions after partial cytoreduction with cytarabine. An initial phase I trial demonstrated that a single infusion of ²²⁵Ac-lintuzumab could be given safely at doses upto 111 kBq/kg with antileukemic activity across all dose levels. A second phase I study showed that fractionated-dose ²²⁵Ac-lintuzumab could be safely combined with low-dose cytarabine and produced objective responses in 28% of older patients with untreated AML. In a phase II study, treatment with ²²⁵Ac-lintuzumab monotherapy for a similar patient population resulted in remission in 69% of patients receiving two fractions of 74 kBq/kg and 22% of patients receiving two 55.5-kBq/kg fractions. Additionally, TAT may be useful in intensifying antileukemic therapy prior to hematopoietic cell transplantation, and pretargeting strategies offer the possibility for improved tumor-to-normal organ dose ratios.