Vemurafenib and Rituximab in Patients with Hairy Cell Leukemia Previously Treated with Moxetumomab Pasudotox

Single agent vemurafenib or rituximab-vemurafenib combination for the treatment of relapsed/refractory hairy cell leukemia, a multicenter experience

BACKGROUND

Hairy cell leukemia (HCL) is a rare mature B-cell malignancy that is primarily treated with purine analogues. However, relapse remains a significant challenge, prompting the search for alternative therapies. The BRAF V600E mutation prevalent in HCL patients provides a target for treatment with vemurafenib.

PATIENTS AND METHODS

This multicenter retrospective study included nine patients with relapsed/refractory (R/R) HCL from six different centers. Patient data included demographics, prior treatments, clinical outcomes, and adverse events.

RESULTS

Patients received different treatment regimens between centers, including vemurafenib alone or in combination with rituximab. Despite the differences in protocols, all patients achieved at least a partial response, with seven patients achieving a complete response. Adverse events were generally mild with manageable side effects. The absence of myelotoxic effects and manageable side effects make BRAF inhibitors attractive, especially for patients ineligible for purine analogues or those with severe neutropenia.

CONCLUSION

Single agent vemurafenib or in combination with rituximab appears to be a promising therapeutic option for R/R HCL. Further research is needed to establish standardized treatment protocols and to investigate long-term outcomes.

Hairy cell leukemia 2024: Update on diagnosis, risk-stratification, and treatment-Annual updates in hematological malignancies

DISEASE OVERVIEW

Hairy cell leukemia (HCL) and HCL-like disorders, including HCL variant (HCL-V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogenous group of mature lymphoid B-cell disorders characterized by the identification of hairy cells, a specific genetic profile, a different clinical course and the need for appropriate treatment.

DIAGNOSIS

Diagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of 3 or 4 based on the CD11c, CD103, CD123, and CD25 expression, the trephine biopsy which makes it possible to specify the degree of tumoral bone marrow infiltration and the presence of BRAFV600E somatic mutation.

RISK STRATIFICATION

Progression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood, and the immunoglobulin heavy chain variable region gene mutational status. VH4-34 positive HCL cases are associated with a poor prognosis, as well as HCL with TP53 mutations and HCL-V.

TREATMENT

Patients should be treated only if HCL is symptomatic. Chemotherapy with risk-adapted therapy purine analogs (PNAs) are indicated in first-line HCL patients. The use of chemo-immunotherapy combining cladribine (CDA) and rituximab (R) represents an increasingly used therapeutic approach. Management of relapsed/refractory disease is based on the use of BRAF inhibitors (BRAFi) plus R, MEK inhibitors (MEKi), recombinant immunoconjugates targeting CD22, Bruton tyrosine kinase inhibitors (BTKi), and Bcl-2 inhibitors (Bcl-2i). However, the optimal sequence of the different treatments remains to be determined.

Dabrafenib plus trametinib in patients with relapsed/refractory BRAF V600E mutation-positive hairy cell leukemia

BRAF V600E is the key oncogenic driver mutation in hairy cell leukemia (HCL). We report the efficacy and safety of dabrafenib plus trametinib in patients with relapsed/refractory BRAF V600E mutation-positive HCL. This open-label, phase 2 study enrolled patients with BRAF V600E mutation-positive HCL refractory to first-line treatment with a purine analog or relapsed after ≥2 prior lines of treatment. Patients received dabrafenib 150 mg twice daily plus trametinib 2 mg once daily until disease progression, unacceptable toxicity, or death. The primary endpoint was investigator-assessed objective response rate (ORR) per criteria adapted from National Comprehensive Cancer Network-Consensus Resolution guidelines. Secondary endpoints included duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Fifty-five patients with BRAF V600E mutation-positive HCL were enrolled. The investigator-assessed ORR was 89.0% (95% confidence interval, 77.8%-95.9%); 65.5% of patients had a complete response (without minimal residual disease [MRD]: 9.1% [negative immunohistochemistry of bone marrow {BM} biopsy], 12.7% [negative BM aspirate flow cytometry {FC}], 16.4% [negative immunohistochemistry and/or FC results]; with MRD, 49.1%), and 23.6% had a partial response. The 24-month DOR was 97.7% with 24-month PFS and OS rates of 94.4% and 94.5%, respectively. The most common treatment-related adverse events were pyrexia (58.2%), chills (47.3%), and hyperglycemia (40.0%). Dabrafenib plus trametinib demonstrated durable responses with a manageable safety profile consistent with previous observations in other indications and should be considered as a rituximab-free therapeutic option for patients with relapsed/refractory BRAF V600E mutation-positive HCL. This trial is registered at www.clinicaltrials.gov as #NCT02034110.

Measurable residual disease in hairy cell leukemia: Technical considerations and clinical significance

Hairy cell leukemia (HCL) is a rare type of chronic lymphoid leukemia originating from a mature B lymphocyte. A diagnosis of HCL is based on cytology, confirmed by multiparametric flow cytometry (MFC) studies using anti-B-cell monoclonal antibodies, together with a panel of antibodies more specific to HCL, such as CD11c, CD25, CD103 and CD123. Recently, the BRAF V600E mutation has been described as a disease-defining genetic event. Measurable residual disease (MRD) is defined as the lowest level of HCL cells that can be detected accurately and reproducibly using validated methods; as MRD negativity is associated with high rates of durable complete response, by clearing MRD, the long-term outcome may be improved in patients with advanced HCL. MRD is typically detected using bone marrow, and in some cases, peripheral blood; however, in HCL, discrepancies frequently exist between MRD results obtained from blood, bone marrow aspirate and core biopsy. Among the methods used for MRD detection, MFC appears to be a more sensitive technique than immunohistochemistry. Molecular tests are also used, such as real-time quantitative PCR for unique immunoglobulin heavy chain (IgH) gene rearrangements and PCR techniques with clone specificity for BRAF V600E. Clone-specific PCR (spPCR) is able to detect one HCL cell in 106 normal cells, and is particularly suitable for patients found to be negative for MRD by MFC. Recently, the Hairy Cell Leukemia Consortium created a platform to work on a definition for MRD, and establish the optimal time point, tissue type and method for measuring MRD. This

Long-term follow-up of cladribine treatment in hairy cell leukemia: 30-year experience in a multicentric Italian study

Hairy cell leukemia (HCL) is a rare lymphoproliferative disease with an excellent prognosis after treatment with cladribine (2CDA), although relapse may occur during follow-up. The aim of the study is to review the efficacy, safety, long-term remission rate, and overall survival (OS) in those patients who received 2CDA as first-line treatment. We retrospectively reviewed data of HCL patients treated with 2CDA between March 1991 and May 2019 at 18 Italian Hematological centers: 513 patients were evaluable for study purpose. The median age was 54 years (range 24–88) and ECOG was 0 in 84.9% of cases. A total of 330 (64.3%) patients received 2CDA intravenously and 183 (35.7%) subcutaneously. ORR was 91.8%: CR was obtained in 335 patients (65.3%), PR in 96 (18.7%), and hematological response in 40 (7.8%) patients; in 42 (8.2%) no response was observed. Hemoglobin value (p = 0.044), frequency of circulating hairy cells (p = 0.039), recovery of absolute neutrophil count (p = 0.006), and normalization of spleen (p ≤ 0.001) were associated with CR compared to PR in univariable analysis. At a median follow-up of 6.83 years (range 0.04–28.52), the median time to relapse was 12.2 years. A significant difference in duration of response was identified between patients that obtained a CR and PR (19.4 years versus 4.8 years, p < 0.0001). Non-hematological grade 3 or higher early toxicity was reported in 103 (20.1%) patients. Median OS was not reached: 95.3%, 92.4%, and 81.8% of patients were estimated to be alive at 5, 10, and 15 years, respectively. Forty-nine patients died (9.5%), following an infection in 14 cases (2.7%), natural causes in 14 (2.7%), cardiovascular events in 13 (2.5%), a second neoplasm in 6 (1.2%), and progression of HCL in 2 cases (0.4%). Following treatment of HCL with 2CDA, 80% of patients are estimated to be alive 15 years after diagnosis.

Intraductal administration of transferrin receptor-targeted immunotoxin clears ductal carcinoma in situ in mouse models of breast cancer-a preclinical study

The human transferrin receptor (TFR) is overexpressed in most breast cancers, including preneoplastic ductal carcinoma in situ (DCIS). HB21(Fv)-PE40 is a single-chain immunotoxin (IT) engineered by fusing the variable region of a monoclonal antibody (HB21) against a TFR with a 40 kDa fragment of Pseudomonas exotoxin (PE). In humans, the administration of other TFR-targeted immunotoxins intrathecally led to inflammation and vascular leakage. We proposed that for treatment of DCIS, intraductal (i.duc) injection of HB21(Fv)-PE40 could avoid systemic toxicity while retaining its potent antitumor effects on visible and occult tumors in the entire ductal tree. Pharmacokinetic studies in mice showed that, in contrast to intravenous injection, IT was undetectable by enzyme-linked immunosorbent assay in blood following i.duc injection of up to 3.0 μg HB21(Fv)-PE40. We demonstrated the antitumor efficacy of HB21(Fv)-PE40 in two mammary-in-duct (MIND) models, MCF7 and SUM225, grown in NOD/SCID/gamma mice. Tumors were undetectable by In Vivo Imaging System (IVIS) imaging in intraductally treated mice within 1 wk of initiation of the regimen (IT once weekly/3 wk, 1.5 μg/teat). MCF7 tumor-bearing mice remained tumor free for up to 60 d of observation with i.duc IT, whereas the HB21 antibody alone or intraperitoneal IT treatment had minimal/no antitumor effects. These and similar findings in the SUM225 MIND model were substantiated by analysis of mammary gland whole mounts, histology, and immunohistochemistry for the proteins Ki67, CD31, CD71 (TFR), and Ku80. This study provides a strong preclinical foundation for conducting feasibility and safety trials in patients with stage 0 breast cancer.

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.

Hairy cell leukemia 2022: Update on diagnosis, risk-stratification, and treatment

DISEASE OVERVIEW

Hairy cell leukemia (HCL) and HCL-like disorders, including HCL variant (HCL-V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogeneous group of mature lymphoid B-cell disorders characterized by the identification of hairy cells, a specific genetic profile, a different clinical course, and the need for appropriate treatment.

DIAGNOSIS

Diagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of 3 or 4 based on the CD11C, CD103, CD123, and CD25 expression, the trephine biopsy which makes it possible to specify the degree of tumoral medullary infiltration and the presence of BRAF^V600E somatic mutation.

RISK STRATIFICATION

Progression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood, and the immunoglobulin heavy chain variable region gene mutational status. VH4-34-positive HCL cases are associated with a poor prognosis.

TREATMENT

Patients should be treated only if HCL is symptomatic. Chemotherapy with risk adapted therapy purine analogs (PNAs) are indicated in first-line HCL patients. The use of chemo-immunotherapy combining PNAs and rituximab (R) represents an increasingly used therapeutic approach. Management of relapsed/refractory disease is based on the use of BRAF inhibitors (BRAFi) plus rituximab or MEK inhibitors (MEKi), recombinant immunoconjugates targeting CD22 or Bruton Tyrosine Kinase inhibitors (BTKi). However, the optimal sequence of the different treatments remains to be determined. The Bcl2-inhibitors (Bcl-2i) can play a major role in the future.

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.

How to Diagnose and Treat CD5-Positive Lymphomas Involving the Spleen

Patients with CD5-expressing lymphomas presenting with splenomegaly are frequently diagnosed with chronic lymphocytic leukemia. The most important differential diagnosis is mantle cell lymphoma, both in its classical and leukemic, non-nodal forms, given its prognostic and therapeutic implications. Other small B-cell neoplasms that frequently involve the spleen and occasionally express CD5 include the splenic marginal zone lymphoma, hairy cell leukemia and, rarely, lymphoplasmacytic lymphoma. The frequency of CD5 positivity depends in part on the sensitivity of the detection methods employed. Usually, a combination of morphological, immunophenotypic and molecular findings allows for a precise sub-classification of CD5-positive, low-grade B-cell lymphomas of the spleen. Some of these tumors may display a mixture of small and larger B cells, raising the possibility of more aggressive lymphomas, such as diffuse large B-cell lymphomas (DLBCL). Approximately 5-10% of DLBCL are CD5-positive and some may manifest as primary splenic lesions. When available, the morphology of DLBCL in the splenic tissue is distinctive and a leukemic picture is very rare. In conclusion, the appropriate morphological and clinical context assisted by flow cytometry panels and/or immunohistochemistry allows the differential diagnosis of CD5-positive, non-Hodgkin, B-cell lymphomas involving the spleen.

Hairy cell leukemia: a brief update on current knowledge and treatment prospects

PURPOSE OF REVIEW

This article provides a brief update on the recommended diagnosis and treatment strategies for patients with the classic form of hairy cell leukemia (HCL) and HCL variant (HCLv).

RECENT FINDINGS

HCL is a chronic B-cell malignancy with multiple treatment options. In recent years, many novel drugs have been assessed for HCL treatment with promising results. The investigated nonchemotherapy options include moxetumomab pasudotox, which targets CD22; vemurafenib or dabrafenib, which target the BRAFV600E protein; trametinib, which targets mitogen-activated protein kinase enzyme; and ibrutinib, which targets Bruton tyrosine kinase.

SUMMARY

Purine analogs significantly improve survival in patients with HCL. However, patients often relapse, require multiple treatments, and may become refractory. The introduction of novel agents has expanded the spectrum of therapy possibilities in those patients. In the coming years, they will assist standard therapy for patients with HCL who may currently have suboptimal results.