Cotreatment of hairy cell leukemia and melanoma with the BRAF inhibitor dabrafenib

How I treat refractory/relapsed hairy cell leukemia with BRAF inhibitors

Hairy cell leukemia (HCL) responds very well to frontline chemotherapy with purine analogs (cladribine and pentostatine). However, approximately half of patients experience 1 or more relapses, which become progressively resistant to these myelotoxic and immunosuppressive agents. At progression, standard therapeutic options include a second course of purine analogs alone or in combination with rituximab and, upon second relapse, therapy with the anti-CD22 immunotoxin moxetumomab pasudotox. Furthermore, blockade of the mutant BRAF-V600E kinase (the pathogenetic hallmark of HCL) through orally available specific inhibitors (vemurafenib or dabrafenib) effaces the peculiar morphologic, phenotypic, and molecular identity of this disease and its typical antiapoptotic behavior and is emerging as an attractive chemotherapy-free strategy in various clinical scenarios. These include patients with, or at risk of, severe infections and, in a highly effective combination with rituximab, patients with relapsed or refractory HCL. Other treatments explored in clinical trials are BTK inhibition with ibrutinib and co-inhibition of BRAF (through dabrafenib or vemurafenib) and its downstream target MEK (through trametinib or cobimetinib). Here, we focus on our experience with BRAF inhibitors in clinical trials and as off-label use in routine practice by presenting 3 challenging clinical cases to illustrate their management in the context of all available treatment options.

Diagnosis and treatment of hairy cell leukemia as the COVID-19 pandemic continues

Hairy cell leukemia (HCL) is an indolent B-cell malignancy, usually driven by the BRAF V600E mutation. For 30 years, untreated and relapsed HCL was successfully treated with purine analogs, but minimal residual disease (MRD) remained in most patients, eventually causing relapse. Repeated purine analogs achieve decreasing efficacy and increasing toxicity, particularly to normal T-cells. MRD-free complete remissions (CRs) are more common using rituximab with purine analogs in both 1^st-line and relapsed settings. BRAF inhibitors and Ibrutinib can achieve remission, but due to persistence of MRD, must be used chronically to prevent relapse. BRAF inhibition combined with Rituximab can achieve high MRD-free CR rates. Anti-CD22 recombinant immunotoxin moxetumomab pasudotox is FDA-approved in the relapsed setting and is unique in achieving high MRD-free CR rates as a single-agent. Avoiding chemotherapy and rituximab may be important in ensuring both recovery from COVID-19 and successful COVID-19 vaccination, an area of continued investigation.

BRAF p.V600E associated poly-neoplastic syndrome

We report a male patient who developed eight different cancers between ages 57 and 64. BRAF p.V600E mutation was detected in Langerhans cell histiocytosis, chronic lymphocytic leukemia, histiocytic sarcoma, melanoma, and adenocarcinoma of the lung. It was not detected in multiple myeloma, basal cell carcinoma, and papillary thyroid cancer. BRAF p.V600E was not detected in normal skin tissue biopsy indicating that BRAF V600E was a somatic mutation affecting cancer cells. The presence of eight different cancers with five of them positive for BRAF p.V600E in a single patient is unprecedented. This type of BRAF p.V600E-associated poly-neoplastic syndrome has never been reported in the medical literature.

Classic hairy cell leukemia complicated by pancytopenia and severe infection: a report of 3 cases treated with vemurafenib

Infections are a major cause of morbidity and mortality in HCL patients, and myelosuppressive therapies increase the risk of poor outcomes. Vemurafenib achieves rapid hematologic improvement in HCL and may facilitate management during life-threatening infection.

Hairy cell leukemia: present and future directions

Hairy cell leukemia (HCL) is an indolent B-cell malignancy, with long-term responses to purine analogs, but with decreasing efficacy and increasing toxicity with repeated courses. Leukemic cells express CD22, CD20, CD25, tartrate-resistant acid phosphatase (TRAP), annexin 1A (Anxa1), and BRAF V600E mutation. HCLv, lacking CD25, Anxa1, TRAP, and BRAF V600E, is more aggressive and less purine analog-sensitive. A molecularly defined IGHV4-34+ variant is also resistant whether HCL or HCLv immunophenotypically. Traces of HCL cells, termed minimal residual disease (MRD), accompany most with complete remission (CR) and may cause relapse. Rituximab has limited single-agent activity, but frequent CR without MRD when combined with purine analog, albeit with chemotherapy toxicities. The anti-CD22 recombinant immunotoxin Moxetumomab Pasudotox can achieve MRD-negative CR in multiply relapsed HCL without chemotherapy toxicities and was FDA approved in 2018 as Lumoxiti. Investigational oral non-chemotherapy options also include Vemurafenib or Dabrafenib/Trametinib targeting BRAF V600E ± MEK, and Ibrutinib targeting Bruton's tyrosine kinase.

New treatment options in hairy cell leukemia with focus on BRAF inhibitors

Hairy cell leukemia (HCL) responds initially very well to chemotherapy with purine analogues. However, up to 50% of patients relapse, often multiple times, and become progressively less sensitive to these myelotoxic and immune-suppressive drugs. At progression, viable therapeutic strategies include addition of rituximab to purine analogues, and treatment with the anti-CD22 immunotoxin moxetumomab pasudotox, which has been recently approved by the FDA in HCL patients after at least two prior therapies. Identification of the BRAF-V600E kinase mutation as the genetic cause of HCL has opened the way, in the relapsed/refractory experimental setting, to targeted and non-myelotoxic effective strategies that are based on inhibition of BRAF with vemurafenib, co-inhibition of BRAF and its target MEK with dabrafenib and trametinib, and BRAF inhibition with vemurafenib combined with anti-CD20 immunotherapy. In particular, vemurafenib plus rituximab is emerging as a short, safe, chemotherapy-free regimen able to induce deep complete remissions in most HCL patients refractory to, or relapsed multiple times, after chemo(immuno)therapy.

BRAF in the cross-hairs

INTRODUCTION

Hairy cell leukemia (HCL) is a rare, chronic B-cell lymphoproliferative disorder characterized by distinctive morphologic features and an indolent clinical course. The discovery of a recurrent activating mutation in BRAF (BRAF V600E) as a disease-defining genetic event in HCL has substantial diagnostic and therapeutic implications. Areas covered: Herein the authors review the role of BRAF V600E and RAF-MEK-ERK signaling in the pathogenesis of HCL, anecdotal clinical reports of BRAF inhibitor monotherapy in management of relapsed or refractory HCL, larger phase 2 trials investigating efficacy of BRAF inhibitor therapy for HCL, adverse effects commonly associated with BRAF inhibitor therapy, including cutaneous toxicity, and mechanisms of therapeutic resistance. Expert opinion: Ongoing and planned studies will help to optimize the use of BRAF inhibitor therapy for HCL by determining the efficacy of BRAF inhibition in combination with other antigen targeted or molecularly targeted therapies, and more broadly, to determine how hematologists can best utilize and sequence emerging diagnostic and therapeutic modalities in the care of patients with newly diagnosed and relapsed or refractory HCL.

BRAF V600E Mutation in Multiple Primary Malignancies: A Hairy Affair

As the number of cancer survivors grows, so does the number of co-occurring primary malignancies and secondary malignancies. In rare cases, single driver mutations can be responsible for concomitant primary malignancies. By understanding the mechanisms that drive multiple primary malignancies (MPM), clinicians are capable of targeting molecular pathways that drive oncogenesis resulting in the successful treatment of many malignancies while also reducing the side effects of conventional chemotherapy. Herein, we report a case of co-occurring hairy cell leukemia (HCL) and malignant melanoma in a 69-year-old male. This patient tested positive for the BRAF V600E mutation and was initiated on a single agent, vemurafenib. He, unfortunately, succumbed to his illness before completion of his planned therapy course.  This case report is intended to highlight the rare co-occurrence of BRAF-positive HCL and melanoma and to encourage driver mutation evaluation when a patient presents with MPM and the possibility of a unifying driver mutation. To the best of our knowledge, this is the first case of a co-occurring BRAF positive melanoma and HCL to be reported in a chemotherapy-naïve patient.

Update on hairy cell leukemia

Hairy cell leukemia (HCL) is a chronic B-cell malignancy with multiple treatment options, including several that are investigational. Patients present with pancytopenia and splenomegaly, owing to the infiltration of leukemic cells expressing CD22, CD25, CD20, CD103, tartrate-resistant acid phosphatase (TRAP), annexin A1 (ANXA1), and the BRAF V600E mutation. A variant lacking CD25, ANXA1, TRAP, and the BRAF V600E mutation, called HCLv, is more aggressive and is classified as a separate disease. A molecularly defined variant expressing unmutated immunoglobulin heavy variable 4-34 (IGHV4-34) is also aggressive, lacks the BRAF V600E mutation, and has a phenotype of HCL or HCLv. The standard first-line treatment, which has remained unchanged for the past 25 to 30 years, is single-agent therapy with a purine analogue, either cladribine or pentostatin. This approach produces a high rate of complete remission. Residual traces of HCL cells, referred to as minimal residual disease, are present in most patients and cause frequent relapse. Repeated treatment with a purine analogue can restore remission, but at decreasing rates and with increasing cumulative toxicity. Rituximab has limited activity as a single agent but achieves high complete remission rates without minimal residual disease when combined with purine analogues, albeit with chemotherapy-associated toxicity. Investigational nonchemotherapy options include moxetumomab pasudotox, which targets CD22; vemurafenib or dabrafenib, each of which targets the BRAF V600E protein; trametinib, which targets mitogen-activated protein kinase enzyme (MEK); and ibrutinib, which targets Bruton tyrosine kinase (BTK).

Concomitant Non-Small Cell Lung Cancer and Hairy Cell Leukemia in a Patient Harboring BRAF-V600E Mutation in Both Tissues: A Case Report

The BRAF-V600E mutation has been established as a signature alteration occurring almost universally in hairy cell leukemia. Moreover, it can be detected in a small percentage of patients with non-small cell lung cancer. We report the case of a patient with a metastatic BRAF-V600E-mutated lung adenocarcinoma suffering from concomitant hairy cell leukemia. The identification of an identical BRAF mutation in both malignancies raises physiopathological considerations and might offer unique therapeutic strategies for this group of patients.

An extremely rare case of concurrent BRAF V600E mutation driven hairy cell leukemia and melanoma: case report and review of literature

BRAF protein is a serine/threonine kinase with 766 amino acids. Approximately 15% of human cancers harbor BRAF mutations as well as other BRAF anomalies (amplifications, fusions). Somatic mutations mainly occur in the catalytic kinase domain (CR3), and the predominant mutation is p.V600E which is the substitution of glutamic acid (E) for valine (V) as result of a mutation at codon 600 of the kinase domain. To our knowledge, the vast majority of the cancers have non-germline BRAF mutations. Here we describe a case of a 60-year-old female with a history of hairy cell leukemia (HCL) who presented with aphasia and forgetfulness. A follow-up Brain CT scan showed three distinct brain lesions which were found to be diagnostic of melanoma (confirmed by immunohistochemistry) with no evidence of a concurrent brain involvement by a B-cell neoplasm. Molecular studies confirmed the same BRAF p.V600E mutation in both malignancies (hairy cell leukemia and melanoma). Thereafter the patient was started on BRAF inhibitor treatment and is now symptom-free after one year of follow up. Having two concurrent malignancies with a shared BRAF mutation is extremely rare and makes this an excellent example of a genomic marker-driven treatment in two histologically and immunophenotypically distinct tumors.

Consensus guidelines for the diagnosis and management of patients with classic hairy cell leukemia

Hairy cell leukemia is an uncommon hematologic malignancy characterized by pancytopenia and marked susceptibility to infection. Tremendous progress in the management of patients with this disease has resulted in high response rates and improved survival, yet relapse and an appropriate approach to re-treatment present continuing areas for research. The disease and its effective treatment are associated with immunosuppression. Because more patients are being treated with alternative programs, comparison of results will require general agreement on definitions of response, relapse, and methods of determining minimal residual disease. The development of internationally accepted, reproducible criteria is of paramount importance in evaluating and comparing clinical trials to provide optimal care. Despite the success achieved in managing these patients, continued participation in available clinical trials in the first-line and particularly in the relapse setting is highly recommended. The Hairy Cell Leukemia Foundation convened an international conference to provide common definitions and structure to guide current management. There is substantial opportunity for continued research in this disease. In addition to the importance of optimizing the prevention and management of the serious risk of infection, organized evaluations of minimal residual disease and treatment at relapse offer ample opportunities for clinical research. Finally, a scholarly evaluation of quality of life in the increasing number of survivors of this now manageable chronic illness merits further study. The development of consensus guidelines for this disease offers a framework for continued enhancement of the outcome for patients.

BRAF V600E mutation in hairy cell leukemia: from bench to bedside

Hairy cell leukemia (HCL) is a distinct clinicopathological entity whose underlying genetic lesion has remained a mystery for over half a century. The BRAF V600E mutation is now recognized as the causal genetic event of HCL because it is somatic, present in the entire tumor clone, detectable in almost all cases at diagnosis (encompassing the whole disease spectrum), and stable at relapse. BRAF V600E leads to the constitutive activation of the RAF-MEK-extracellular signal-regulated kinase (ERK) signaling pathway which represents the key event in the molecular pathogenesis of HCL. KLF2 and CDNK1B (p27) mutations may cooperate with BRAF V600E in promoting leukemic transformation. Sensitive molecular assays for detecting BRAF V600E allow HCL (highly responsive to purine analogs) to be better distinguished from HCL-like disorders, which are treated differently. In vitro preclinical studies on purified HCL cells proved that BRAF and MEK inhibitors can induce marked dephosphorylation of MEK/ERK, silencing of RAF-MEK-ERK pathway transcriptional output, loss of the HCL-specific gene expression profile signature, change of morphology from “hairy” to “smooth,” and eventually apoptosis. The overall response rate of refractory/relapsed HCL patients to the BRAF inhibitor vemurafenib approached 100%, with 35% to 40% complete remissions (CRs). The median relapse free-survival was about 19 months in patients who had achieved CR and 6 months in those who had obtained a partial response. Future therapeutic perspectives include: (1) combining BRAF inhibitors with MEK inhibitors or immunotherapy (anti-CD20 monoclonal antibody) to increase the percentage of CRs and (2) better understanding of the molecular mechanisms underlying resistance of HCL cells to BRAF inhibitors.

Novel Drugs and Combination Therapies for the Treatment of Metastatic Melanoma

Metastatic melanoma (MM) still remains as one of the most worrisome cancer known to mankind. In last two decades, treatment of melanoma took a dramatic turn with the discovery of targeted therapy which targets the mutations in mitogen-activated protein kinase (MAPK) pathway and immune checkpoint inhibitors. These new findings have led to emergence of many novel drugs that have been approved by FDA. Targeted therapy drugs such as vemurafenib, trametinib and dabrafenib target the MAPK pathway whereas immunotherapies such as ipilimumab, nivolumab and pembrolizumab block immune checkpoint receptors on T lymphocytes. All these drugs have shown to improve the overall survival in MM. Despite these recent discoveries, treatment of MM remains challenging because of rapid development of resistance to targeted therapy. This review will discuss recently approved drugs and their adverse effects and also shed light on combination therapy in treatment of melanoma.

Targeting Mutant BRAF in Relapsed or Refractory Hairy-Cell Leukemia

BACKGROUND

BRAF V600E is the genetic lesion underlying hairy-cell leukemia. We assessed the safety and activity of the oral BRAF inhibitor vemurafenib in patients with hairy-cell leukemia that had relapsed after treatment with a purine analogue or who had disease that was refractory to purine analogues.

METHODS

We conducted two phase 2, single-group, multicenter studies of vemurafenib (at a dose of 960 mg twice daily)--one in Italy and one in the United States. The therapy was administered for a median of 16 weeks in the Italian study and 18 weeks in the U.S. study. Primary end points were the complete response rate (in the Italian trial) and the overall response rate (in the U.S. trial). Enrollment was completed (28 patients) in the Italian trial in April 2013 and is still open (26 of 36 planned patients) in the U.S. trial.

RESULTS

The overall response rates were 96% (25 of 26 patients who could be evaluated) after a median of 8 weeks in the Italian study and 100% (24 of 24) after a median of 12 weeks in the U.S. study. The rates of complete response were 35% (9 of 26 patients) and 42% (10 of 24) in the two trials, respectively. In the Italian trial, after a median follow-up of 23 months, the median relapse-free survival was 19 months among patients with a complete response and 6 months among those with a partial response; the median treatment-free survival was 25 months and 18 months, respectively. In the U.S. trial, at 1 year, the progression-free survival rate was 73% and the overall survival rate was 91%. Drug-related adverse events were usually of grade 1 or 2, and the events most frequently leading to dose reductions were rash and arthralgia or arthritis. Secondary cutaneous tumors (treated with simple excision) developed in 7 of 50 patients. The frequent persistence of phosphorylated ERK-positive leukemic cells in bone marrow at the end of treatment suggests bypass reactivation of MEK and ERK as a resistance mechanism.

CONCLUSIONS

A short oral course of vemurafenib was highly effective in patients with relapsed or refractory hairy-cell leukemia. (Funded by the Associazione Italiana per la Ricerca sul Cancro and others; EudraCT number, 2011-005487-13; ClinicalTrials.gov number NCT01711632.).

BRAF inhibitor therapy in HCL

Targeted treatment approaches are transforming the therapeutic landscape of cancer care. The discovery of the BRAF V600E mutation in most cases of classical hairy cell leukemia opens up unique opportunities for tumor specific treatment of HCL targeting the MEK/ERK signaling pathway. The discovery and biological implications of BRAF V600E in HCL are summarized to form a basis for our current understanding of the potential for clinical exploitation. There is overwhelming clinical evidence for activity of inhibitors of BRAF in the disease. The review will review current trial activity as well as discuss novel trial concepts exploiting targeted treatment focusing on BRAF inhibition in HCL.

Recent advances in diagnosis and treatment of hairy cell leukemia

Hairy cell leukemia (HCL) is a rare, indolent B-cell lymphoproliferative disorder that accounts for 2% of all cases of leukemia. Most patients present with pancytopenia and splenomegaly with variable number of ‘hairy’ lymphocytes in blood. BRAF V600E mutation can be detected in virtually 100% of HCL cases and is absent in other B-cell lymphomas. The mutated gene and its responding abnormal protein can be used as specific markers in the diagnosis of HCL. New therapeutic modalities targeting on mutated BRAF and its downstream pathways have shown encouraging results in clinical trials. The objective of this review article is to discuss the recent developments in the diagnosis and management of hairy cell leukemia.

Hairy cell leukemia: update and current therapeutic approach

PURPOSE OF REVIEW

In this review, we discuss the pathogenesis and standard therapeutic approach to hairy cell leukaemia (HCL) as well as newer targeted therapies under investigation showing promising end-points in treating HCL.

RECENT FINDINGS

HCL is an indolent B-cell leukaemia. Historically, HCL patients have achieved excellent response to purine nucleoside analogues and single purine analogue treatment with pentostatin or cladribine is currently the standard of care for initial treatment. Most patients achieve complete remission with this form of therapy. However, long-term follow-up has demonstrated that a large number of patients eventually develop relapsed disease. Relapse disease tends to be more difficult to treat and refractory to the same purine analogues. Development of relapsing and refractory disease after initially achieving complete remission with purine analogue treatment has generated a need for alternative therapies.

SUMMARY

Identification of the BRAFV600E mutation in nearly 100% of HCL patients has provided rationale for inclusion of BRAF inhibitors into the therapeutic armamentarium to treat HCL. Clinical trials are currently underway measuring efficacy of vemurafenib in achieving clinical response in relapsed/refractory HCL and also toxicity. Other novel therapies with monoclonal and immunotoxin-conjugated antibodies have also shown promising response in recent investigational studies.