The Virtual Conference on

Challenges in Hematology

Waldenstrom’s Macroglobulinemia (MW) is an indolent lymphoproliferative disorder characterized by the histologic evidence of bone marrow involvement by lymphoplasmacytic lymphoma and the presence of an IgM monoclonal component.  Importantly the mutation of the myeloid differentiation primary-response gene 88 (MYD88), in about 90% of patients, and the CXCR4 mutation that can be found in about 30-45% of cases, may play a role on the therapeutic decision. Patients carrying CXCR4 mutation have longer time to responses, less deep responses and shorter progression free survival when treated with ibrutinib. The asymptomatic patient only needs regular follow-up. Treatment depends on patients characteristics, type of symptoms, presence or not of bulky disease and above all on the speed with which control of the disease is required. Patients presenting with hyperviscosity syndrome should undergo immediate plasmapheresis and initiate systemic therapy immediately. Immuno-chemotherapy, bendamustine based (BendaR), cyclophospamide based (DRC) or bortezomib in combination with rituximab are the recommended fixed duration treatments in first line. Ibrutinib exerts favourable results in first line and should be considered in patients unfit for immuno-chemotherapy and in those without CXCR4 mutation. The administration of a continuous treatment should be carefully weighed. In unfit very elderly patients monotherapy with chlorambucil, fludarabine and rituximab monotherapy may still have a role.  In relapsed disease, if the response to first line has been prolonged, it may be considered to repeat the same therapy. The best results in the salvage setting are certainly obtained with the BTKis. In a phase 2 study a 54% 5-year disease-free survival has been obtained with ibrutinib in heavily pretreated. The randomized Innovate trial, which compared rituximab plus placebo versus rituximab plus ibrutinib confirmed the efficacy in patients treated with a BTK inhibitor, importantly the addition of rituximab resulted in a better outcome independent from CXCR4 mutation. Second generation BTKis, acalabruitnib and zanubrutinib, have shown non inferior efficacy with a more favourable toxic prophile. Several agents are under development in WM, second generation proteasome inhibitors, carfilzomib and ixazomib, are effective leading to good quality of responses with better toxic profile when compared to bortezomib. Trials are ongoing to evaluate chemo-free treatments with fixed duration regimens.

Minimal Residual Disease (MRD) is today a hot topic also in lymphomas (NHL). Indeed, the availability of new drugs and more sensitive techniques allows now to achieve a good clearance of MRD. In 2018, FDA stated that MRD had to be included in the results necessary for approving new drugs, but, differently from other hematological malignancies, MRD did not still entered into the clinical practice in the context of NHLs. Nevertheless, many pivotal trials put MRD among their research goals. In follicular lymphoma, several studies, including FOLL05, PRIMA, GALLIUM, ZEUS etc…, clearly demonstrated that MRD condition PFS, across different treatment schedules. In mantle cell lymphoma, it has been reported a significant impact of MRD, especially in the high-dose therapy where some gene polymorphisms are able to condition the results from lenalidomide maintenance. In Waldenstrom’s Macroglobulinemia, MYD88 is a good marker of MRD, especially when assessed on plasma circulating cell-free DNA. In DLBCL, MRD has been shown to be predictive of response and survival, especially when applied to the “liquid biopsy” (cf-DNA, extracellular vesicles).

In the last years, also the improvement of molecular techniques helped to put attention to MRD: indeed, in addition to quantitative PCR (ASO-PCR), clonality of IGH, TCR and light chains can be assessed by NGS, that represents an “unsupervised” technique, able to identify also clones absent at diagnosis but that might sustain relapse. NGS has got a sensitivity of 1-3% and is useful also for identifying the mutational background of NHLs. Digital PCR is another new technique that is a quantitative PCR that does not need a reference external curve, with a high sensitivity (1×10-5) and accuracy. This method is able to quantitate about 25% of samples defined “positive but not quantifiable” by the “classic” real-time PCR.

The integration of all these techniques probably will significantly increase the role of MRD detection in NHLs.

The landscape of multiple myeloma (MM) has changed considerably in the past two decades regarding new treatments, insight into disease biology and innovation in the techniques available to assess measurable residual disease (MRD) as the most accurate method to evaluate treatment efficacy. The sensitivity and standardization achieved by these techniques together with unprecedented rates of complete remission (CR) induced by new regimens, raised enormous interest in MRD as a surrogate biomarker of patients’ outcome and endpoint in clinical trials. By contrast, there is reluctance and general lack of consensus on how to use MRD outside clinical trials. I will discuss critical aspects related with the implementation of MRD in clinical practice.

Natural killer (NK) cells are lymphocytes belonging to the innate immune system. Their cytotoxic activity is tightly regulated by the balanced expression of a wide and complicated pattern of activating and inhibitory receptors, among which inhibitory receptors called killer-immunoglobulin like receptors (KIRs) have been extensively characterized. In cancer immunology, especially in leukemias,  NK cells have been shown to mediate antitumor immune-surveillance both in solid tumours and haematological malignancies. Indeed, NK cells are potent effectors which can target and kill leukemia cells without prior exposure to those cells. Particularly, NK cells have a major role in the eradication of residual acute myeloid leukemia (AML)  cells after haploidentical stem cell transplantation (SCT), boosting graft-versus-leukemia (GVL) effects without exacerbating graft-versus-host disease (GVHD). Several groups have sought to translate this notion to the non-transplantation setting by using infusion of NK cells as a means of adoptive immunotherapy for patients with cancers. Based on their crucial role, several strategies of NK cell-based immunotherapy, i.e. freshly isolated, in vitro expanded and/or activated, gene-modified by using the CAR-based approach, have been investigated at the preclinical level with important and promising early clinical results. Our group reported the feasibility and early clinical efficacy of selecting and infusing highly purified, T cell-depleted, KIR-mismatched NK cells to consolidate remission in high-risk patients with AML. The percentage of donor-derived alloreactive NK cell clones before infusion was significantly correlated with relapse occurrence, indicating that a functional dose of 2 x10⁵/kg alloreactive NK cells may be predictive of response. Based on these data, a multicentre clinical trial of adoptive immunotherapy with haplodentical KIR-L mismatched alloreactive NK cells to consolidate remission in AML patients not eligible for allogeneic SCT is currently on-going (NCT03955848).

My talk will summarize the most relevant evidence supporting the translational use of of NK cells as a mean of adoptive immunotherapy against hematological malignancies with a special focus on AML.