Durable responses to ibrutinib in patients with relapsed CLL after allogeneic stem cell transplantation

The role of allogeneic hematopoietic cell transplantation for chronic lymphocytic leukemia: A review

Although the use of allogeneic hematopoietic cell transplantation (HCT) for chronic lymphocytic leukemia (CLL) has declined with the development of novel targeted agents, it continues to play an important role for eligible patients with high-risk or heavily pretreated CLL who lack other treatment options. CLL is susceptible to a potent graft-versus-leukemia (GVL) effect which produces long-lasting remissions in 30-50% of transplanted patients. While allogeneic HCT is associated with significant risks of graft-versus-host disease (GVHD), infection, and non-relapse mortality (NRM), improvements in patient and donor selection, reduced intensity conditioning (RIC), GVHD prophylaxis, and supportive care have rendered this an increasingly safe and effective procedure in the current era. In this review, we discuss recent advances in allogeneic HCT for CLL, with a focus on the optimal evidence-based strategies to maximize benefit and minimize toxicity of this potentially curative cellular therapy.

Efficacy of minimal residual disease driven immune-intervention after allogeneic hematopoietic stem cell transplantation for high-risk chronic lymphocytic leukemia: results of a prospective multicenter trial

Allogeneic hematopoietic stem cell transplantation (HSCT) remains a potentially curative and useful strategy in high-risk relapsing chronic lymphocytic leukemia (CLL). Minimal residual disease (MRD) assessment at 12 months (M12) post-HSCT is predictive of relapse. This phase II study aimed to achieve M12 MRD negativity (MRDneg) using an MRD-driven immune-intervention (Md-PII) algorithm based on serial flow-cytometry blood MRD, involving cyclosporine tapering followed in case of failure by donor lymphocytes infusions. Patients had high-risk CLL according to the 2006 European Society for Blood and Marrow Transplantation consensus, in complete or partial response with lymphadenopathy <5 cm and comorbidity score ≤2. Donors were HLA-matched sibling or matched unrelated (10/10). Fortytwo enrolled patients with either 17p deletion (front-line, n=11; relapse n=16) or other high-risk relapse (n=15) received reduced intensity-conditioning regimen before HSCT and were submitted to Md-PII. M12- MRDneg status was achieved in 27 of 42 patients (64%) versus 6 of 42 (14.2%) before HSCT. With a median follow-up of 36 months (range, 19-53), 3-year overall survival, non-relapse mortality and cumulative incidence of relapse are 86.9% (95% Confidence Interval [CI]: 70.8-94.4), 9.5% (95% CI: 3.7-23.4) and 29.6% (95% CI: 17.3-47.7). Incidence of 2-year limited and extensive chronic graft versus host disease (cGVHD) is 38% (95% CI: 23-53) and 23% (95% CI: 10-36) including two cases post Md-PII. Fifteen patients converted to MRDneg either after cyclosporine A withdrawal (n=12) or after cGvHD (n=3). As a time-dependent variable, MRDneg achievement at any time-point correlates with reduced relapse (Hazard ratio [HR] 0.14 [range, 0.04-0.53], P=0.004) and improvement of both progression free (HR 0.18 [range, 0.06-0.6], P<0.005) and overall (HR 0.18 [range, 0.03-0.98], P=0.047) survival. These data highlight the value of MRD-driven immune-intervention to induce prompt MRD clearance in the therapy of CLL (clinicaltrials gov. Identifier: NCT01849939).

Refractory and 17p-deleted chronic lymphocytic leukemia: improving survival with pathway inhibitors and allogeneic stem cell transplantation

Refractory/early relapsed and 17p deletion/p53 mutation (del(17p)/TP53mut)-positive chronic lymphocytic leukemia (CLL) has been conventionally considered a high-risk disease, potentially eligible for treatment with allogeneic stem cell transplantation (alloSCT). In this multicenter retrospective analysis of 157 patients, we compared the outcomes of patients with high-risk CLL treated with alloSCT, a B-cell receptor pathway inhibitor (BCRi), and both. Seventy-one patients were treated with BCRis, 67 patients underwent reduced-intensity conditioning alloSCT, and 19 received alloSCT with a BCRi before and/or after transplantation. Inverse probability of treatment weighting analyses were performed to compare the alloSCT and no-alloSCT groups; in the 2 groups, 5-year OS, PFS, and cumulative incidence of nonrelapse mortality (NRM) and relapse were 40% versus 60% (P = .096), 34% versus 17% (P = .638), 28% versus 5% (P = .016), and 38% versus 83% (P = .005), respectively. Patients treated with alloSCT plus BCRi had a 3-year OS of 83%. The 3-year OS and NRM by year of alloSCT, including patients treated with BCRi, were 53% and 17% in 2000 to 2007, 55% and 30% in 2008 to 2012, and 72% and 18% in 2013 to 2018. In conclusion, the combination of pathway inhibitors and alloSCT is feasible and may further improve the outcome of high-risk CLL patients.

Allogeneic transplantation for high-risk chronic lymphocytic leukemia-a summary of a 16-year experience

In the pathway inhibitor era, the number of allogeneic stem cell transplantation (ASCT) for chronic lymphocytic leukemia (CLL) continues to decrease and this approach should be offered only after careful risk-benefit assessment. Nevertheless, ASCT still remains only curative therapeutic modality for CLL, especially in countries with limited access to novel agents. Thirty patients with CLL at median age of 42 years at diagnosis (range 29-64) underwent ASCT between years 2002 and 2018. Thirteen patients were transplanted in complete remission (CR), ten patients achieved partial response (PR), and seven had stable disease. The median time from diagnosis to transplant was 4 years (range 0.5-12). Twenty-three patients received HLA-matched related donor stem cell grafts, and seven patients received either matched unrelated donor or HLA-mismatched grafts. Reduced intensity conditioning (RIC) and myeloablative regimen (MAC) were used in 24 and 6 patients, respectively. Mortality to day + 100 after transplant was 16% (8% for RIC only). Acute and chronic graft versus host disease (GVHD) developed in 40% and 63% of patients, respectively. Fifteen patients relapsed or progressed after transplant. Thirteen patients (43%) are alive at last follow-up and 10 (77%) remain in clinical CR. Median follow-up for survivors was 6.8 years (range 0.4-15.2). Three-year progression-free and overall survivals were 56% and 60%, respectively. These outcomes were better for patients who received RIC conditioning: 64% and 72%, respectively. CR at transplant was found to have favorable impact on post-allograft survival. RIC should be preferred over MAC. ASCT may remain a valuable option for some CLL patients.

High-risk chronic lymphocytic leukemia in the era of pathway inhibitors: integrating molecular and cellular therapies

High-risk chronic lymphocytic leukemia (CLL) has been defined by clinical and/or genetic resistance (TP53 abnormalities) to treatment with chemoimmunotherapy (CIT). With the availability of pathway inhibitors (PIs), such as kinase inhibitors and BCL2 antagonists, the outlook of CIT-resistant patients has dramatically improved. Here, we propose a revision of the concept of high-risk CLL, driven by TP53 abnormalities and response to treatment with PI. CLL high-risk-I, CIT-resistant is defined by clinically CIT-resistant disease with TP53 aberrations, but fully responsive to PI. This category is largely the domain of PI-based therapy, and cellular therapy (ie, allogeneic hematopoietic cell transplantation) remains an option only in selected patients with low individual procedure-related risk. In CLL high-risk-II, CIT- and PI-resistant, characterized by increasing exhaustion of pharmacological treatment possibilities, cellular therapies (including chimeric antigen receptor-engineered T cells) should be considered in patients eligible for these procedures. Moreover, molecular and cellular therapies are not mutually exclusive and could be used synergistically to exploit their full potential.

A Patient with Non-Hodgkin Lymphoma and Nonspecific Interstitial Pneumonia during Ibrutinib Therapy

We present a 74-year-old male with nonspecific interstitial pneumonia (NSIP) during treatment with ibrutinib for mantle cell lymphoma. Previously, the patient had received six cycles of bendamustine and rituximab and six cycles of R-CHOP, followed by rituximab maintenance therapy. Respiratory tract complications of ibrutinib other than infectious pneumonia have not been mentioned in larger trials, but individual case reports hinted to a possible association with the development of pneumonitis. In our patient, the onset of alveolitis that progressed towards NSIP together with the onset of ibrutinib treatment suggests causality. One week after ibrutinib was discontinued, nasal symptoms resolved first. A follow-up CT showed a reduction in the reticular hyperdensities and ground-glass opacities, suggestive of restitution of the lung disease. To our knowledge, this is the first case showing a strong link between ibrutinib and interstitial lung disease, strengthening a previous report on subacute pneumonitis. Our findings have clinical implications because pulmonary side effects were reversible at this early stage. We, therefore, suggest close monitoring for respiratory side effects in patients receiving ibrutinib.

[Preventative and therapeutic relapse strategies after allogeneic hematopoietic stem cell transplantation: Guidelines from the Francophone society of bone marrow transplantation and cellular therapy (SFGM-TC)]

Disease relapse remains the first cause of mortality of hematological malignancies after allogeneic hematopoietic stem cell transplantation (allo-HCT). The risk of recurrence is elevated in patients with high-risk cytogenetic or molecular abnormalities, as well as when allo-HCT is performed in patients with refractory disease or with persistent molecular or radiological (PET-CT scan) residual disease. Within the frame of the 7th annual workshops of the francophone society for bone marrow transplantation and cellular therapy, the working group reviewed the literature in order to elaborate unified guidelines for the prevention and treatment of relapse after allo-HCT. For high risk AML and MDS, a post transplant maintenance strategy is possible, using hypomethylating agents or TKI anti-FLT3 when the target is present. For Philadelphia positive ALL, there was a consensus for the use of post-transplant TKI maintenance. For lymphomas, there are no strong data on the use of post-transplant maintenance, and hence a preemptive strategy is recommended based on modulation of immunosuppression, close follow-up of donor chimerism, and donor lymphocytes infusion. For multiple myeloma, even though the indication of allo-HCT is controversial, our recommendation is post transplant maintenance using bortezomib, due to its a good toxicity profile without increasing the risk of GVHD.

Current Status of Bruton's Tyrosine Kinase Inhibitor Development and Use in B-Cell Malignancies

The B-cell receptor (BCR) pathway plays an important role in the survival, proliferation and trafficking of cancer cells in a variety of B-cell malignancies. Recently, a number of agents have been developed to target various components of the BCR pathway. One such target is Bruton's tyrosine kinase (BTK), a Tec family kinase member found near the cell membrane that is involved in upstream BCR signaling. The biological function of BTK in several B-cell lymphoid malignancies has led to the development of the oral BTK inhibitor ibrutinib. In chronic lymphocytic leukemia (CLL), ibrutinib has demonstrated durable clinical responses in relapsed/refractory (R/R) patients, including those with the high-risk del(17p) cytogenetic abnormality. These findings have paved the way for trials evaluating ibrutinib in previously untreated CLL patients, and also in combination with chemoimmunotherapy or other novel agents. Durable clinical responses have also been demonstrated in mantle cell lymphoma (MCL) and Waldenström's macroglobulinemia (WM) patients treated with ibrutinib. Ibrutinib is generally well tolerated, although current follow-up remains short and patients of advanced age are more likely to discontinue treatment for toxicity. Treatment-specific side effects such as bleeding and atrial fibrillation may, at least partly, be related to off-target inhibition of non-BTK kinases. Studies evaluating other potential indications for BTK inhibition are ongoing, including in post-allogeneic hematopoietic stem cell transplant patients for whom ibrutinib may be effective in modulating graft-versus-host disease. Combination trials of ibrutinib with venetoclax, a Bcl-2 inhibitor, are underway and are supported by sound preclinical rationale. Several next-generation BTK inhibitors are under development with the goal of decreasing treatment-related toxicity and resistance.

Successful Treatment of Richter Transformation with Ibrutinib in a Patient with Chronic Lymphocytic Leukemia following Allogeneic Hematopoietic Stem Cell Transplant

Patients with chronic lymphocytic leukemia (CLL) who progress to Richter transformation (RT) have a poor prognosis. Multi-agent chemotherapy regimens do not have good response rates. There are few case reports on the use of ibrutinib in RT. Here, we present a patient who was heavily pretreated for CLL, including allogeneic stem cell transplant, and progressed to RT. She had a mixed response to multi-agent chemotherapy and was started on ibrutinib. She had a complete response for 16 months on single-agent ibrutinib with minimal toxicity.

Risk factors for treatment failure after allogeneic transplantation of patients with CLL: a report from the European Society for Blood and Marrow Transplantation

For young patients with high-risk CLL, BTK-/PI3K-inhibitors or allogeneic stem cell transplantation (alloHCT) are considered. Patients with a low risk of non-relapse mortality (NRM) but a high risk of failure of targeted therapy may benefit most from alloHCT. We performed Cox regression analyses to identify risk factors for 2-year NRM and 5-year event-free survival (using EFS as a surrogate for long-term disease control) in a large, updated EBMT registry cohort (n= 694). For the whole cohort, 2-year NRM was 28% and 5-year EFS 37%. Higher age, lower performance status, unrelated donor type and unfavorable sex-mismatch had a significant adverse impact on 2-year NRM. Two-year NRM was calculated for good- and poor-risk reference patients. Predicted 2-year-NRM was 11 and 12% for male and female good-risk patients compared with 42 and 33% for male and female poor-risk patients. For 5-year EFS, age, performance status, prior autologous HCT, remission status and sex-mismatch had a significant impact, whereas del(17p) did not. The model-based prediction of 5-year EFS was 55% and 64%, respectively, for male and female good-risk patients. Good-risk transplant candidates with high-risk CLL and limited prognosis either on or after failure of targeted therapy should still be considered for alloHCT.

Ibrutinib efficacy and tolerability in patients with relapsed chronic lymphocytic leukemia following allogeneic HCT

Ibrutinib, a potent and irreversible small-molecule inhibitor of both Bruton's tyrosine kinase and interleukin-2 inducible kinase (ITK), has been used to treat relapsed/refractory chronic lymphocytic leukemia (CLL) with prolongation of progression-free and overall survival. Here, we present 27 patients with relapsed CLL following allogeneic hematopoietic cell transplant (HCT) who subsequently received ibrutinib salvage therapy. Sixteen of these patients were part of multi-institutional clinical trials and achieved an overall response rate of 87.5%. An additional 11 patients were treated at Stanford University following US Food and Drug Administration approval of ibrutinib; 7 (64%) achieved a complete response, and 3 (27%) achieved a partial response. Of the 9 patients treated at Stanford who had mixed chimerism-associated CLL relapse, 4 (44%) converted to full donor chimerism following ibrutinib initiation, in association with disease response. Four of 11 (36%) patients evaluated by ClonoSeq achieved minimal residual disease negativity with CLL <1/10 000 white blood cells, which persisted even after ibrutinib was discontinued, in 1 case even after 26 months. None of the 27 patients developed graft-versus-host-disease (GVHD) following ibrutinib initiation. We postulate that ibrutinib augments the graft-versus-leukemia (GVL) benefit through a T-cell-mediated effect, most likely due to ITK inhibition. To investigate the immune modulatory effects of ibrutinib, we completed comprehensive immune phenotype characterization of peripheral B and T cells from treated patients. Our results show that ibrutinib selectively targets pre-germinal B cells and depletes Th2 helper cells. Furthermore, these effects persisted after drug discontinuation. In total, our results provide evidence that ibrutinib effectively augments GVL without causing GVHD.

Reappraising the timing of transplant for indolent non-Hodgkin lymphomas

INTRODUCTION

Indolent non-Hodgkin lymphomas (iNHL) remain incurable with standard approaches. The timing of autologous stem cell transplant (ASCT) is changing following the introduction of new drugs that can potentially defer the transplant, improved reduced intensity conditioning (RIC) and haploidentical allogeneic SCT (allo-SCT).

AREAS COVERED

The most relevant aspects concerning the role of hematopoietic stem cell transplantation in the management of iNHL are discussed. Literature search methodology included examination of PubMed index and meeting presentations. Expert commentary: ASCT is not currently employed as consolidation in first-line, being reserved to patients with refractory/relapsed disease. The curative potential of graft-versus-lymphoma (GVL) after RIC allo-SCT could be particularly beneficial in patients with iNHL relapsing after ASCT. This scenario could be modified in the near future by better definition of high-risk patients at diagnosis, by the improvement of minimal residual disease (MRD) evaluation and by the introduction of new drugs in the therapeutic algorithm.