ALBERT

Description: BACKGROUND AND AIMS: Hairy cell leukemia (HCL) is very sensitive to purine analogs (PAs), but ~40% of patients relapse and become progressively less responsive to these myelotoxic and immune-suppressive drugs. Having discovered the BRAF-V600E kinase-activating mutation as the genetic lesion underlying HCL (Tiacci et al, NEJM 2011;364:2305), we performed the first clinical trial of a BRAF inhibitor (vemurafenib) in refractory/relapsed HCL. In particular, this is a phase-2, academic, single-arm, Italian, multi-center (n=8) study (HCL-PG01; EudraCT 2011-005487-13). METHODS: In 11 months we enrolled 28 BRAF-V600E+ HCL patients, needing therapy due to cytopenias and including: i) 6 patients primary refractory to a PA; ii) 21 patients who relapsed early and/or repeatedly after PAs and had received a median of 4 previous therapies; and iii) a 81-year old patient showing severe myelotoxicicity after a PA (discouraging its further use). Previous treatments other than PAs included interferon, rituximab and splenectomy in 12, 14 and 8 patients, respectively. Complete remission (CR) required resolution of cytopenias (N≥1500/mmc, PLT≥100000/mmc, Hb≥11 g/dl), no morphological evidence of HCL cells in the bone marrow biopsy and blood smear, and no splenomegaly. Partial remission (PR) required resolution of cytopenias, and a ≥50% reduction of splenomegaly and of marrow and blood HCL involvement by immunophenotyping. Two patients were not evaluable as they went off-study after ≤1 week of treatment (due to drug-unrelated acute myocardial infarction and consent withdrawal after grade-3 drug-related reversible pancreatitis). RESULTS: Vemurafenib, given orally at the dose of 960 mg twice daily on an outpatient basis for a median of 16 weeks, was generally well tolerated. Drug-related adverse events (mainly arthralgias, skin toxicities, pancreatitis; no myelosuppression) were frequent, but reversible in all patients, and were typically grade 1-2. Only 7 patients developed grade 3 events, and none grade 4 events. Although we did not observe any cutaneous squamous cell carcinomas/keratoachantomas (as reported in BRAF-V600E+ melanoma patients treated with vemurafenib), 3 patients developed 2 basaliomas and 1 superficial melanoma, all treated with a simple excision. Notably, overall response rate was 96% (25/26 patients): 9/26 (34.6%) CRs and 16/26 (61.4%) PRs, obtained after a median of 8 and 9 weeks respectively. CR and PR patients included 1 and 5 primary refractory ones, respectively, as well as 4 and 10 not responding to the last prior treatment, respectively. In all CR patients immunohistochemistry showed minimal residual disease (≤10%) at the end of treatment. Six of 9 (67%) CR patients enjoyed normal blood counts at a median of 13 (range 12-15) months from the end of treatment (see Figure): 3 of these 6 patients showed no morphological evidence of HCL in the bone marrow biopsy (complying with a continuous CR) at 12, 13 and 15 months, respectively, whereas the other 3 lost the bone marrow CR status, all at 12 months. The remaining 3/9 CR patients (33%) developed a mild cytopenia (N ~1000/mmc or PLT ~80000/mmc) 5, 9 and 12 months post-treatment, respectively: in the 2nd patient the cytopenia remained stable until the last follow-up at 15 months, whereas in the other two cases it worsened requiring therapy 9 and 18 months post-treatment, respectively (see Figure). These two latter patients were recently retreated with vemurafenib for 12 and 4 weeks, and obtained a PR and a second CR. Among the 16 PR patients, 5 (31%) mantain normal blood counts at a median of 12 (range 8-17) months post-treatment (see Figure). The other 11 PR patients developed cytopenia(s) after 3 months of median follow-up (range 5-10): in 6 patients (38%) no anti-leukemic therapy was started at a median of 9 (range 6-12) months post-treatment, whereas in the remaining 5 cases (31%) cytopenia(s) worsened requiring therapy at a median of 8 (range 5-11) months of follow-up (see Figure). Four of these latter 5 patients were retreated with vemurafenib for 12 weeks: 3 cases had a minor response and the last one witnessed a second PR that lasted less than the first PR (3 versus 9 months). CONCLUSIONS: In heavily pre-treated HCL patients, a short oral course of vemurafenib was safe, and proved quickly and highly active. Retreatment with vemurafenib was able to reinduce remissions in patients relapsing after a CR, but was less effective in patients relapsing after a PR. Figure 1 Figure 1. Disclosures Off Label Use: Off-label use of vemurafenib in hairy cell leukemia will be discussed as part of a clinical research protocol..

Description: Among acute myeloid leukemia (AML) patients with a normal karyotype (CN-AML), NPM1 and CEBPA mutations define World Health Organization 2008 provisional entities accounting for approximately 60% of patients, but the remaining 40% are molecularly poorly characterized. Using whole-exome sequencing of one CN-AML patient lacking mutations in NPM1, CEBPA, FLT3-ITD, IDH1, and MLL-PTD, we newly identified a clonal somatic mutation in BCOR (BCL6 corepressor), a gene located on chromosome Xp11.4. Further analyses of 553 AML patients showed that BCOR mutations occurred in 3.8% of unselected CN-AML patients and represented a substantial fraction (17.1%) of CN-AML patients showing the same genotype as the AML index patient subjected to whole-exome sequencing. BCOR somatic mutations were: (1) disruptive events similar to the germline BCOR mutations causing the oculo-facio-cardio-dental genetic syndrome; (2) associated with decreased BCOR mRNA levels, absence of full-length BCOR, and absent or low expression of a truncated BCOR protein; (3) virtually mutually exclusive with NPM1 mutations; and (4) frequently associated with DNMT3A mutations, suggesting cooperativity among these genetic alterations. Finally, BCOR mutations tended to be associated with an inferior outcome in a cohort of 422 CN-AML patients (25.6% vs 56.7% overall survival at 2 years; P = .032). Our results for the first time implicate BCOR in CN-AML pathogenesis.

Description: BACKGROUND: Hairy cell leukemia (HCL) responds well to purine analogs, but up to 50% of patients relapse. We previously identified the BRAF-V600E mutation as the genetic lesion underlying HCL (NEJM 364:230-2315, 2011), and successfully targeted this mutation in the clinic with the oral BRAF inhibitor vemurafenib through an academic phase-2 multi-center Italian trial in HCL patients relapsed after or refractory to purine analogs (NEJM 373:1733-1747, 2015). In these heavily pre-treated patients, vemurafenib given for a median of 16 weeks produced 96% of responses, including 9/26 (35%) complete remissions (CR) and 16/26 (61%) partial remissions (PR), which were obtained after a median of 8 weeks of treatment. Even in complete responders, immunohistochemistry showed residual (~10%) bone marrow HCL cells at the end of treatment, and relapses were common, occurring at a median of 19 months and 6 months in CR and PR patients respectively. Residual HCL cells resisting vemurafenib treatment might be targeted by concomitant immunotherapy with an anti-CD20 monoclonal antibody, an attractive strategy to potentially achieve a more profound response and a better clinical outcome through a chemotherapy-free approach. METHODS: We started an academic, phase-2, single-center trial (EudraCT 2014-003046-27) in relapsed/refractory HCL, which tests vemurafenib in combination with rituximab, another targeted non-myelotoxic drug with known single-agent activity in HCL. Eligibility was extended to patients relapsed also after monotherapy with a BRAF inhibitor. Vemurafenib was given at its standard dose (960 mg twice daily orally) for 8 weeks. Rituximab infusions (375 mg/m2intravenously) were given concomitantly with vemurafenib every 2 weeks, as well as sequentially (after the end of vemurafenib dosing) four times every 2 weeks. RESULTS: We have so far enrolled 22 patients in 16 months. Adverse reactions were reversible, usually mild and consistent with the known toxicity profile of the two drugs when used alone. Notably, a CR was achieved by all 14 patients already evaluable for efficacy (100%), including 4 who had relapsed after a BRAF inhibitor and 1 previously refractory to rituximab. Furthermore, 12/14 patients (86%) obtained the CR as early as after 4 weeks of vemurafenib and 2 concomitant rituximab infusions. This CR rate appears higher than that observed by us and others using vemurafenib alone in BRAF inhibitor-naive patients relapsed after or refractory to purine analogs (CR rate 35-42%; NEJM 373:1733-1747, 2015). Moreover, minimal residual disease (MRD) was undetectable in the bone marrow biopsy and aspirate of 8/11 patients evaluated (73%), both by immunophenotyping and by allele-specific PCR (limit of detection: 0.05% BRAF-V600E copies). In 5 of these 8 patients, MRD clearing was reached even before sequential rituximab dosing post-vemurafenib. In the remaining 3/11 patients, MRD was at most 5% in 2 vemurafenib-naive patients, and 10% in 1 patient relapsed after prior BRAF-inhibitor treatment. In contrast, residual bone marrow disease was a constant feature of all 26 patients treated by us with vemurafenib alone for a longer time period (NEJM 373:1733-1747, 2015). CONCLUSIONS: This study - which is the first one combining vemurafenib and rituximab in relapsed/refractory HCL - suggests that this non-myelotoxic regimen produces more numerous, faster and deeper CRs than vemurafenib alone. Enrollment continues. Disclosures Gaidano: Karyopharm: Consultancy, Honoraria; Morphosys: Consultancy, Honoraria; Roche: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau.

Description: Abstract 4135 Acute myeloid leukemia (AML) expressing mutated NPM1 gene and cytoplasmic nucleophosmin (NPMc+ AML) [Falini B et al, NEJM 2005;352:254-266] is a new entity of WHO classification that shows distinctive biological and clinical features. AML with mutated NPM1 usually presents with a high white blood cell count; the bone marrow biopsy is usually markedly hypercellular and leukemic cells frequently show myelomonocytic or monocytic features, with dysplasia and involvement of two or more cell lineages in about 25% of cases. Lack, or low expression, of CD34 in over 90% of cases is the most distinctive immunophenotypic feature of NPM1-mutated AML and is independent of leukemic cell maturation. NPM1 gene mutation without concomitant FLT3-ITD identify a subgroup of AML patients with a favorable prognosis and has been associated with an approximately 50-60% probability of survival at 5 years in younger patients. Here we report 4 out of 41 (10%) patients, admitted at our Hospital in the last year, with new-diagnosed AML with mutated NPM1 presenting with life-threatening thromboembolic (either arterial or venous) events. The main characteristics of these patients are summarized in Table 1. The patients had neither personal nor family history concerning thromboembolism. Hyperleukocytosis was a common feature of the vast majority of NPM1-mutated AML patients at diagnosis. Immunophenotypic analysis did not show a peculiar phenotype in these patients. Table 1 Characteristics of patients with NPM1-mutated AML and thrombosis. Case report no Age Sex (M/F) FAB subtype WBC/mmc Type of thrombosis Site of thrombosis 1 41 F M1 14970 arterial Anterior interventricular branch of left coronary artery 2 56 M M4 93990 arterial external iliac and femoral (right limb) 3 63 M M2 113000 deep venous great saphenous veins (bilateral) 4 73 F M4 190000 deep venous iliac and femoral In two patients (cases 1 and 2), the arterial thromboembolic event (acute myocardial infarction and acute ischemia of right lower limb, respectively) presented about one month before diagnosis of leukemia. In the other 2 patients (cases 3 and 4), deep venous thromboembolism was concomitant with the diagnosis of leukemia. One patient (case 4), who could not initiate chemotherapy for severe concomitant renal failure, died few days after diagnosis. The other patients recovered from the acute event and upon diagnosis of leukemia were promptly treated with standard polychemotherapy which allowed to obtain complete hematological remission associated with complete resolution of the thromboembolic event. The clinical course after chemotherapeutic treatment of the patients outlines the importance and life saving role of early chemotherapy even under adverse circumstances. The pathogenesis of thromboembolic disease in hematological malignancies is complex and multifactorial: tumor cell-derived procoagulant, fibrinolytic or proteolytic factors and inflammatory cytokines affect clotting activation. Other important factors include infectious complications and hyperleukocytosis. However, large vessel thrombosis is a very rare clinical presentation. Our report of severe thromboembolic events at presentation in AML with mutated NPM1 suggests some still unidentified biological features of this leukemia which we are currently investigating. Disclosures: No relevant conflicts of interest to declare.