A novel clofarabine bridge strategy facilitates allogeneic transplantation in patients with relapsed/refractory leukemia and high-risk myelodysplastic syndromes

The added value of multi-state modelling in a randomized controlled trial: The HOVON 102 study re-analyzed

Clofarabine is an active antileukemic drug for subgroups of patients with acute myeloid leukemia (AML). Multi-state models can provide additional insights to supplement the original intention-to-treat analysis of randomized controlled trials (RCT). We re-analyzed the HOVON102/SAKK30/09 phase III RCT for newly diagnosed AML patients, which randomized between standard induction chemotherapy with or without clofarabine. Using multi-state models, we evaluated the effects of induction chemotherapy outcomes (complete remission [CR], measurable residual disease [MRD]), and post-remission therapy with allogeneic stem cell transplantation [alloSCT] on relapse and death. Through the latter a consistent reduction in the hazard of relapse in the clofarabine arm compared to the standard arm was found, which occurred irrespective of MRD status or post-remission treatment with alloSCT, demonstrating a strong and persistent antileukemic effect of clofarabine. During the time period between achieving CR and possible post-remission treatment with alloSCT, non-relapse mortality was higher in patients receiving clofarabine. An overall net benefit of treatment with clofarabine was identified using the composite endpoint current leukemia-free survival (CLFS). In conclusion, these results enforce and extend the earlier reported beneficial effect of clofarabine in AML and show that multi-state models further detail the effect of treatment on competing and series of events.

Adoptive immunotherapy with CB following chemotherapy for patients with refractory myeloid malignancy: chimerism and response

We conducted a prospective evaluation of cord blood (CB)-derived adoptive cell therapy, after salvage chemotherapy, for patients with advanced myeloid malignancies and poor prognosis. Previously, we reported safety, feasibility, and preliminary efficacy of this approach. We present updated results in 31 patients who received intensive chemotherapy followed by CB infusion and identify predictors of response. To enhance the antileukemic effect, we selected CB units (CBU) with shared inherited paternal antigens and/or noninherited maternal antigens with the recipients. Twenty-eight patients with acute myeloid leukemia (AML), 2 with myelodysplastic syndrome, and 1 in chronic myeloid leukemia myeloid blast crisis were enrolled; 9 had relapsed after allogeneic transplant. Response was defined as <5% blasts in hypocellular bone marrow at 2 weeks after treatment. Thirteen patients (42%) responded; a rate higher than historical data with chemotherapy only. Twelve had CBU-derived chimerism detected; chimerism was a powerful predictor of response (P < .001). CBU lymphocyte content and a prior transplant were associated with chimerism (P < .01). Safety was acceptable: 3 patients developed mild cytokine release syndrome, 2 had grade 1 and 2 had grade 4 graft-versus-host disease. Seven responders and 6 nonresponders (after additional therapy) received subsequent transplant; 5 are alive (follow-up, 5-47 months). The most common cause of death for nonresponders was disease progression, whereas for responders it was infection. CB-derived adoptive cell therapy is feasible and efficacious for refractory AML. Banked CBU are readily available for treatment. Response depends on chimerism, highlighting the graft-versus-leukemia effect of CB cell therapy. This trial was registered at www.clinicaltrials.gov as #NCT02508324.

Haematologic malignancies with unfavourable gene mutations benefit from donor lymphocyte infusion with/without decitabine for prophylaxis of relapse after allogeneic HSCT: A pilot study

Relapse is the main cause of treatment failure for leukaemia patients with unfavourable gene mutations who receive allogeneic haematopoietic stem cell transplantation (allo‐HSCT). There is no consensus on the indication of donor lymphocyte infusion (DLI) for prophylaxis of relapse after allo‐HSCT. To evaluate the tolerance and efficacy of prophylactic DLI in patients with unfavourable gene mutations such as FLT3‐ITD, TP53, ASXL1, DNMT3A or TET2, we performed a prospective, single‐arm study. Prophylactic use of decitabine followed by DLI was planned in patients with TP53 or epigenetic modifier gene mutations. The prophylaxis was planned in 46 recipients: it was administered in 28 patients and it was not administered in 18 patients due to contraindications. No DLI‐associated pancytopenia was observed. The cumulative incidences of grade II–IV and III–IV acute graft‐versus‐host disease (GVHD) at 100 days post‐DLI were 25.8% and 11.0%, respectively. The rates of chronic GVHD, non‐relapse mortality and relapse at 3 years post‐DLI were 21.6%, 25.0% and 26.1%, respectively. The 3‐year relapse‐free survival and overall survival (OS) rates were 48.9% and 48.2%, respectively. Acute GVHD (HR: 2.30, p = 0.016) and relapse (HR: 2.46, p = 0.003) after DLI were independently associated with inferior OS. Data in the current study showed the feasibility of prophylactic DLI with/without decitabine in the early stage after allo‐HSCT in patients with unfavourable gene mutations.

Sequential intensive chemotherapy followed by autologous or allogeneic transplantation for refractory lymphoma

We evaluate the safety of bendamustine as a bridge to stem cell transplantation (SCT) in patients with relapsed/refractory lymphoma and residual disease after salvage therapy. Thirty-four subjects without complete responses (CR) received bendamustine 200 mg/m²/day for 2 days followed 14 days later by SCT. Sixteen subjects in partial remission (PR) with maximal FDG-PET SUVs ≤8 prior to bendamustine received autologous SCT, while 13 with suboptimal responses were allografted. Five subjects did not proceed to transplant. No bendamustine toxicities precluded transplantation and no detrimental effect on engraftment or early treatment-related mortality (TRM) was attributable to bendamustine. At 1 year, 75% of auto-recipients and 31% of allo-recipients were alive with CR. Two subjects in the autologous arm developed therapy-related myeloid neoplasia (t-MN). In conclusion, a bendamustine bridge to SCT can be administered without early toxicity to patients with suboptimal responses to salvage chemotherapy. However this approach may increase the risk of t-MN. (NCT02059239).Supplemental data for this article is available online at here.

Donor lymphocyte infusion for prevention of relapse after unmanipulated haploidentical PBSCT for very high-risk hematologic malignancies

Unmanipulated haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) has been an established treatment to cure high-risk leukemia/lymphoma. Relapse is the main cause of treatment failure for patients with relapsed/refractory disease or with very high-risk gene mutations such as TP53, TET2, and DNMT3a. In this study, we aimed to establish the tolerance and efficacy of prophylactic donor lymphocyte infusion (DLI) with G-CSF-primed peripheral blood progenitors for prevention of relapse in these very high-risk patients after haplo-PBSCT. The prophylactic DLI was given at a median of 77 days after transplantation in 31 of 45 consecutive patients with very high-risk leukemia/lymphoma. The median dose of CD3⁺ cells for infusion was 1.8 × 10⁷/kg. The 100-day incidences of acute graft-versus-host disease (GVHD) grades 2–4 and 3–4 after DLI were 55.3% and 10.2%. The 2-year incidences of chronic GVHD and severe chronic GVHD were 52.0% and 18.2%. The 2-year incidences of non-relapse mortality and relapse were 33.1% and 32.5%. The 2-year probabilities of overall survival and relapse-free survival were 40.1% and 31.9%. Poor-risk gene mutations (p = 0.029), disease in non-remission status prior to transplantation (p = 0.005), and donors older than 40 years of age (p = 0.043) were associated with relapse after DLI. In multivariate analysis, disease in non-remission status prior to transplantation was an independent risk factor of relapse (hazard ratio = 4.079; p = 0.035). These data showed the feasibility of the prophylactic DLI in the haplo-PBSCT setting and the anti-leukemic efficacy in very high-risk leukemia/lymphoma.

The safety and efficacy of clofarabine in combination with high-dose cytarabine and total body irradiation myeloablative conditioning and allogeneic stem cell transplantation in children, adolescents, and young adults (CAYA) with poor-risk acute leukemia

Acute leukemias in children with CR3, refractory relapse, or induction failure (IF) have a poor prognosis. Clofarabine has single agent activity in relapsed leukemia and synergy with cytarabine. We sought to determine the safety and overall survival in a Phase I/II trial of conditioning with clofarabine (doses 40 - 52 mg/m²), cytarabine 1000 mg/m², and 1200 cGy TBI followed by alloSCT in children, adolescents, and young adults with poor-risk leukemia. Thirty-seven patients; Age 12 years (1-22 years); ALL/AML: 34:3 (18 IF, 10 CR3, 13 refractory relapse); 15 related, 22 unrelated donors. Probabilities of neutrophil, platelet engraftment, acute GvHD, and chronic GvHD were 94%, 84%, 49%, and 30%, respectively. Probability of day 100 TRM was 8.1%. 2-year EFS (event free survival) and OS (overall survival) were 38.6% (CI₉₅: 23-54%), and 41.3% (CI₉₅: 25-57%). Multivariate analysis demonstrated overt disease at time of transplant (relative risk (RR) 3.65, CI₉₅: 1.35-9.89, P = 0.011) and umbilical cord blood source (RR 2.17, CI₉₅: 1.33-4.15, P = 0.019) to be predictors of worse EFS/OS. This novel myeloablative conditioning regimen followed by alloSCT is safe and well tolerated in CAYA with very poor-risk ALL or AML. Further investigation in CAYA with better risk ALL and AML undergoing alloSCT is warranted.

Salvaged allogeneic hematopoietic stem cell transplantation for pediatric chemotherapy refractory acute leukemia

There is an ongoing debate concerning the performance of salvaged allogeneic hematopoietic stem cell transplantation (allo-HSCT) in pediatric patients with acute refractory leukemia, in whom the prognosis is quite dismal. Few studies have ever been conducted on this subject. This may be partly due to missed opportunities by majority of the patients in such situations. To investigate the feasibility, evaluate the efficiency, and identify the prognostic factors of allo-HSCT in this sub-setting, the authors performed a single institution-based retrospective analysis. A total of 44 patients, of whom 28 had acute myeloid leukemia (AML), 13 had acute lymphocytic leukemia (ALL), and 3 had mixed phenotype leukemia (MPL), were enrolled in this study. With a median follow-up of 19 months, the estimated 2-year overall survival (OS) and progression free survival (PFS) were 34.3% (95% CI, 17.9–51.4%) and 33.6% (95% CI, 18.0–50.1%), respectively. The estimated 2-year incidence rates of relapse and non-relapse mortality (NRM) were 43.8% (95% CI 26.4–60.0%) and 19.6% (95% CI 9.1–32.9%), respectively. The estimated 100-day cumulative incidence of acute graft versus host disease (aGvHD) was 43.6% (95% CI 28.7–57.5%), and the 1-year cumulative incidence of chronic GvHD (cGvHD) was 45.5% (95% CI 30.5–59.3%). Compared with the previous studies, the multivariate analysis in this study additionally identified that female donors and cGvHD were associated with lower relapse and better PFS and OS. Male recipients, age younger than 10 years, a diagnosis of ALL, and the intermediate-adverse cytogenetic risk group were associated with increased relapse. On the contrary, extramedullary disease (EMD) and aGvHD were only linked to worse PFS. These data suggested that although only one-third of the patients would obtain PFS over 2 years, salvaged allo-HSCT is still the most reliable and best therapeutic strategy for refractory pediatric acute leukemia. If probable, choosing a female donor, better management of aGvHD, and induction of cGvHD promotes patient survival.

Prophylactic Donor Lymphocyte Infusion (DLI) Followed by Minimal Residual Disease and Graft-versus-Host Disease-Guided Multiple DLIs Could Improve Outcomes after Allogeneic Hematopoietic Stem Cell Transplantation in Patients with Refractory/Relapsed Acute Leukemia

Patients with refractory/relapsed acute leukemia who have received allogeneic hematopoietic stem cell transplantation (allo-HSCT) are still at a high risk for relapse post-transplant. To investigate the impact of prophylactic donor lymphocyte infusion (DLI) followed by minimal residual disease (MRD) test and graft-versus-host disease (GVHD)-guided multiple DLIs to prevent relapse and improve survival in patients with refractory/relapsed acute leukemia who received allo-HSCT. A multicenter prospective study was designed. In total, 100 patients who achieved complete remission at 30 days post-transplant and had no uncontrolled infection, organ failure, or active GVHD were eligible First, prophylactic DLI was administered at 30 days after HLA-matched related HSCT or 45 to 60 days after HLA-matched unrelated HSCT or haploidentical HSCT. Subsequently, multiple DLIs were administered based on the results of MRD test and whether they developed GVHD. In addition to DLI, chemotherapy was also given to patients who had a positive MRD test. Three-year cumulative incidence of relapse, leukemia-free survival, and survival post-transplant were 32.4% (95% confidence interval, 22.4% to 42.4%), 50.3% (95% confidence interval, 40.3% to 60.3%), and 51.4% (95% confidence interval, 41.2% to 61.6%), respectively. In multivariate analysis, a positive MRD test (HR, 3.840; 95% confidence interval, 1.678 to 5.784; P= .001) and receiving 1 course of DLI (HR, 4.346; 95% confidence interval, 1.223 to 9.450, P= .023) were associated with an increased relapse risks. These data suggest that prophylactic DLI followed by MRD test and GVHD-guided multiple DLIs reduced relapse and increased survival post-transplant in patients with refractory/relapsed acute leukemia who received allo-HSCT. The study is registered at www.ClinicalTrials.gov as NCT01455272.

Treatment options for patients with myelodysplastic syndromes after hypomethylating agent failure

The treatment of patients with myelodysplastic syndromes (MDSs) has hinged primarily on supportive care (ie, blood transfusions, colony stimulating agents, iron chelation, etc.) and the US Food and Drug Administration-approved agents, including 5-azacytidine, deoxyazacytidine, and lenalidomide. For patients no longer benefitting from these agents, there is a paucity of effective therapies. The challenges at this time include our limited understanding of the mechanisms of resistance to these therapies and the variables employed to select next best therapies for patients based on: (1) their performance status and medical comorbidities; (2) the molecular feature(s) of their MDS; (3) the prior treatments they have received; and (4) the long-term goal(s)/possibilities for their future treatment (ie, transplant vs no transplant).

Metabolism, Biochemical Actions, and Chemical Synthesis of Anticancer Nucleosides, Nucleotides, and Base Analogs

Nucleoside, nucleotide, and base analogs have been in the clinic for decades to treat both viral pathogens and neoplasms. More than 20% of patients on anticancer chemotherapy have been treated with one or more of these analogs. This review focuses on the chemical synthesis and biology of anticancer nucleoside, nucleotide, and base analogs that are FDA-approved and in clinical development since 2000. We highlight the cellular biology and clinical biology of analogs, drug resistance mechanisms, and compound specificity towards different cancer types. Furthermore, we explore analog syntheses as well as improved and scale-up syntheses. We conclude with a discussion on what might lie ahead for medicinal chemists, biologists, and physicians as they try to improve analog efficacy through prodrug strategies and drug combinations.

Haploidentical cord transplantation-The best of both worlds

Haploidentical (haplo)-cord transplantation combines infusion of an umbilical cord blood (UCB) unit with CD34-selected cells usually from human leukocyte antigen (HLA) mismatched donors. Initial rapid count recovery from the haplo-hematopoietic progenitors, is gradually replaced by durable engraftment from UCB progenitors. UCB grafts used for haplo-cord are smaller, but better matched than those required for single or double UCB stem cell transplant (SCT). More than 200 patients with hematological malignancies have been transplanted. Median age was 54 years (range 17-74) and 77 were over age 60. One-year survival was 64% for patients with intermediate- and low-risk disease, with no deaths beyond 2 years. In high-risk disease, 1-year survival was 44%. In a comparison with patients undergoing double UCB SCT, haplo-cord transplant resulted in faster hematopoietic recovery, lower rates of acute and chronic graft-versus-host disease (GVHD), lower rates of disease recurrence, and improved GVHD- and relapse-free survival (GRFS). Excellent results were also reported for patients with aplastic anemia where 18 of 21 patients had sustained cord blood engraftment. Rates of GVHD and of disease recurrence after haplo-cord are encouraging. However, in the approximately 10% of patients with failure of the UCB graft disease recurrence is high, supporting the important role of UCB-mediated graft-versus-leukemia (GVL). Ongoing efforts are aimed at identifying determinants of UCB engraftment, at reducing rates of disease recurrence in high risk patients and at optimizing dose and schedule of ATG -necessary to avoid early haplo-graft rejection, but also contributing to early post-transplant immunocompromise. For those lacking haploidentical donors, unrelated donors have been successfully utilized.

Second Allogeneic Stem Cell Transplantation for Acute Leukemia Using a Chemotherapy-Only Cytoreduction with Clofarabine, Melphalan, and Thiotepa

Relapse after allogeneic hematopoietic stem cell transplantation (alloHSCT) remains one of the leading causes of mortality in patients with leukemia. Treatment options in this population remain limited, with concern for both increased toxicity and further relapse. We treated 18 patients with acute leukemia for marrow ± extramedullary relapse after a previous alloHSCT with a myeloablative cytoreductive regimen including clofarabine, melphalan, and thiotepa followed by a second or third transplantation from the same or a different donor. All patients were in remission at the time of the second or third transplantation. All evaluable patients engrafted. The most common toxicity was reversible transaminitis associated with clofarabine. Two patients died from transplantation-related causes. Seven patients relapsed after their second or third transplanation and died of disease. Nine of 18 patients are alive and disease free, with a 3-year 49% probability of overall survival (OS). Patients whose remission duration after initial alloHSCT was >6 months achieved superior outcomes (3-year OS, 74%, 95% confidence interval, 53% to 100%), compared with those relapsing within 6 months (0%) (P < .001). This new cytoreductive regimen has yielded promising results with acceptable toxicity for second or third transplantations in patients with high-risk acute leukemia who relapsed after a prior transplantation, using various graft and donor options. This approach merits further evaluation in collaborative group studies.

A promising sword of tomorrow: Human γδ T cell strategies reconcile allo-HSCT complications

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is potentially a curative therapeutic option for hematological malignancies. In clinical practice, transplantation associated complications greatly affected the final therapeutical outcomes. Currently, primary disease relapse, graft-versus-host disease (GVHD) and infections remain the three leading causes of a high morbidity and mortality in allo-HSCT patients. Various strategies have been investigated in the past several decades including human γδ T cell-based therapeutical regimens. In different microenvironments, human γδ T cells assume features reminiscent of classical Th1, Th2, Th17, NKT and regulatory T cells, showing diverse biological functions. The cytotoxic γδ T cells could be utilized to target relapsed malignancies, and recently regulatory γδ T cells are defined as a novel implement for GVHD management. In addition, human γδ Τ cells facilitate control of post-transplantation infections and participate in tissue regeneration and wound healing processes. These features potentiate γδ T cells a versatile therapeutical agent to target transplantation associated complications. This review focuses on insights of applicable potentials of human γδ T cells reconciling complications associated with allo-HSCT. We believe an improved understanding of pertinent γδ T cell functions would be further exploited in the design of innovative immunotherapeutic approaches in allo-HSCT, to reduce mortality and morbidity, as well as improve quality of life for patients after transplantation.

Control of relapsed or refractory acute myeloid leukemia by clofarabine in preparation for allogeneic stem cell transplant

Allogeneic stem cell transplant is indicated for patients with refractory or relapsed acute myeloid leukemia (AML). Since elimination of the leukemic load is thought to be a prerequisite for treatment success, we here investigate toxicity and anti-leukemic activity of a clofarabine-AraC salvage protocol preceding transplant. In this retrospective analysis, we observed induction of objective remissions in 86% of patients receiving clofarabine-AraC as compared to 83% with sequential high dose AraC/mitoxantrone (S-HAM) and 50% after mitoxantrone/topotecane/AraC (MTC) salvage strategies. In addition, clofarabine conferred anti-leukemic activity to some patients who failed initial MTC or S-HAM therapy. For overall and leukemia-free survival, we identified cytogenetically defined adverse risk markers but not response to therapy to be a strong predictor. In summary, the clofarabine-AraC salvage strategy combines pronounced anti-leukemic activity with an acceptable toxicity profile and allows the majority of patients with relapsed or refractory AML to proceed to allo-SCT, even in cytogenetically defined high risk situations.

Allogeneic stem cell transplantation for refractory acute myeloid leukemia: a single center analysis of long-term outcome

For patients with refractory acute myeloid leukemia (AML), allogeneic stem cell transplantation (alloSCT) represents the only curative approach. We here analyzed the long-term outcome of 131 consecutive patients with active AML, which was either primary refractory or unresponsive to salvage chemotherapy, transplanted at our center between 1997 and 2013. After a median follow-up of 48 months for the surviving patients, disease-free survival (DFS) at 5 yr post alloSCT was 26% (94% CI: 17-35). Relapses, most of which occurred within the first 2 yr from transplant, were the predominant cause of treatment failure affecting 48% (95%CI: 40-58) of patients, whereas non-relapse mortality was 26% (95%CI: 20-36) at 5 yr and thereafter. A marrow blast count ≥20% before alloSCT was an independent prognosticator associated with an inferior DFS (HR: 1.58, P = 0.027), whereas the development of chronic graft-versus-host disease (cGvHD) predicted an improved DFS (HR 0.21, P < 0.001) and a decreased relapse incidence (HR: 0.18, P = 0.026), respectively. These results indicate that alloSCT represents a curative treatment option in a substantial proportion of patients with refractory AML. A pretransplant blast count <20% before alloSCT and the development of cGvHD are the most important predictors of long-term disease control.

Clofarabine/cyclophosphamide for debulking before stem cell transplantation

BACKGROUND

Allogeneic haematopoietic stem cell transplantation (HSCT) is the only curative rescue therapy for patients (pts) with chemotherapy-refractory acute leukaemia. Disease control prior to HSCT is essential for long-term disease-free survival after HSCT.

PATIENTS AND METHODS

We have retrospectively analysed the outcome of 20 pts aged 21-64 years with refractory leukaemia (acute myeloid leukaemia, n = 16; acute lymphatic leukaemia, n = 4) who received debulking therapy with clofarabine (10 mg/m², days 1-4) and cyclophosphamide (200 mg/m², days 1-4; ClofCy) prior to HSCT.

RESULTS

Clofarabine/cyclophosphamide (1-4 cycles) was well tolerated and resulted in a substantial reduction of leukaemic cells in all pts. HSCT was performed in 15 of 20 pts. After HSCT (myeloablative, n = 9; dose-reduced, n = 6), all pts showed engraftment and full donor chimerism (related donors, n = 4 or unrelated donors, n = 11) and all pts achieved complete haematologic remission (CR). The median survival after HSCT is 531 days (range: 48-1462 days), and six pts are still alive after a median of 1245 days. Seven pts died after they had relapsed between days +152 and +1496. One patient died from acute graft-versus-host disease (day +48) and one from systemic fungal infection (day +87).

CONCLUSION

Clofarabine/cyclophosphamide is a novel effective treatment approach for pts with chemotherapy-refractory acute leukaemia prior to HSCT. Whether this novel debulking protocol leads to improved long-term outcome in pts with refractory leukaemias remains to be determined in forthcoming clinical studies.