Hussein, Kebede

Abstract Abstract 2911 Poster Board II-887 BACKGROUND: Pomalidomide (POM) is an immune modulatory drug (IMiD® Immunomodulatory compound) recently shown to improve anemia in subjects with myelofibrosis (MF) in an adaptive phase-2 trial (0.5 mg or 2.0 mg/d with or without prednisone; Tefferi et. al. JCO 2009)). There were no dose limiting toxicities (DLT) observed. No other MF-features (splenomegaly, fibrosis) were identified/improved even at the highest dose. We performed a subsequent dose-escalation trial to determine whether higher doses of POM are effective and well tolerated. METHODS: The trial was classic 3 × 3 design on pts with symptomatic MF (anemia and/or symptomatic splenomegaly). POM was started at dose of 2.5 mg/days (d) for 21 d every 28 d. Dose increased in cohorts by 0.5 mg/d were done if no subject had a DLT (≥grade-4 hematologic toxicity, ≥grade-3 febrile neutropenia or ≥grade-3 non-hematologic toxicity) in cycle-1. Subsequent cohorts were enrolled until the maximum tolerated dose (MTD) was reached (dose level before that resulting in DLT in >1 of 6 subjects). In the phase 2 portion, subjects were treated at the MTD, those without response at the MTD after 3 cycles were lowered to the minimal effective dose (MED) of 0.5mg/d. RESULTS: Subjects: 19 subjects with MF were enrolled 06/2008-03/2009. 14 had primary MF, 3 post-polycythemia vera MF, and 2 post-essential thrombocythemia MF. Median age was 67 y (range, 43-83 y), 11 were female (58%). 16 had a JAK2-V617F mutation. 11 were RBC-transfusion–dependent (58%). 16 subjects had palpable splenomegaly, median 12.5 cm below the LCM (range, 1-26 cm). Median time since diagnosis was 24 mo (range, 1-173 mo). 15 were considered intermediate-high risk by IWG-MRT IPSS (Cervantes et al, Blood, 2009). Phase-1: 3 subjects each were enrolled at the 2.5 mg/d, 3.0 g/d, and 3.5 g/d mg dose cohorts. A DLT (bone marrow suppression) was seen at the 3.5 mg/d level. 3 additional subjects received 3.0 mg/d level cohort confirming this dose as the MTD. Phase-2: 10 additional subjects were enrolled at the MTD of 3.0mg/d. No improvement in anemia was seen, possibly because of bone marrow suppression. Consequently, the dose was decreased to 0.5mg/d in 7 subjects (2 remain on 3.0mg). 9 subjects remain on POM (all but 2 at 0.5mg/d. 104 cycles have been given (median, 4/ subject; range, 2-11). 10 subjects, all at ≥2.5mg/d discontinued because of lack of response/ withdrawal of consent (N=5), progression (N=4) or unrelated worsening co-morbidities (N=1). Toxicity: Dose-related bone marrow suppression was the main toxicity. 10/19 subjects had grade-3/-4 neutropenia (N=8) and/or thrombocytopenia (=3) and was only observed at doses ≥2.5mg/d. No substantial bone marrow suppression at 0.5m/d. Non-hematologic toxicity was uncommon at any dose level with grade-3 fatigue at 3.0mg/d in 1 subject. Efficacy: There was clinical benefit in 9 subjects. 7 subjects achieved an IWG-MRT response (Tefferi et al, Blood, 2006) including clinical improvement (CI) in anemia (N=6; rbc-transfusion-independence or hemoglobin increase >2g/dL for ≥2 mo) and/or splenomegaly (N=2; ≥50% reduction of palpable component for ≥2 months). 2 subjects had improved anemia below the IWG-MRT CI-threshold. Clinical benefit occurred after a median of 3.8 mo (range, 2.1-9.2 mo), and only after reduction to 0.5mg/d in 7 responders including both with spleen responses. There were 2 responses amongst 11 subjects receiving ≥2.5 mg/d compared to 7 of 8 subjects receiving '1.0mg/d. These responses occurred a median of 1 cycle after dose reduction (1-3 months). Responses were durable: 8 of 9 responders continue on-study. CONCLUSIONS: In subjects with myelofibrosis, POM doses ≥2 mg/d are associated with moderate to severe bone marrow suppression. Response occurred at doses ≥2 mg/d primarily after dose reduction to 0.5 mg/d where bone marrow suppression was infrequent. The authors suggest 0.5 mg/d as the preferred doses for a phase-3 trial. Disclosures: Litzow: Enzon: Honoraria, Research Funding.

Abstract Abstract 2909 Poster Board II-885 Background: Previous studies have identified sole abnormalities of del(20q) and del(13q) as prognostically favorable cytogenetic markers in primary myelofibrosis (PMF) (Tefferi et al. BJH 2001;113:763). A more recent study (Tam et al. Blood 2009;113:4171) confirmed these findings and suggested additional cytogenetic markers of prognosis. In the current study with larger numbers of informative patients studied at time of diagnosis, we wanted to validate these observations and examine the prognostic interaction between cytogenetic risk categorization and the International Prognostic Scoring System (IPSS). Methods: Patients with cytogenetic information at diagnosis were selected from the Mayo Clinic database of WHO-defined PMF. Specific cytogenetic categories were considered only in the presence of at least 5 informative patients; otherwise, they were included in the category of “other cytogenetic abnormalities”. Follow-up information was updated in July, 2009. Survival curves were prepared by the Kaplan-Meier method and compared by the log-rank test. Cox regression model was used for multivariable analysis. Results: 200 patients were studied (median age, 62 years; 63% males). The IPSS risk distributions were low in 66 patients, intermediate (int)-1 in 64, int-2 in 44 and high in 26. Cytogenetic findings at diagnosis were abnormal in 83 (42%) patients and included sole del(20q) in 21, complex (i.e. 3 or more abnormalities) in 13, sole del(13q) in 8, sole +8 in 7, sole +9 in 6, and other abnormalities in 28 patients. Median survivals in low, int-1, int-2 and high IPSS risk groups were 188, 71, 47 and 26 months, respectively (p < 0.0001). Median survival in patients with sole +9 was not reached and in those with sole del(13q), sole del(20q), normal karyotype, complex abnormalities and sole +8 was 112, 108, 80, 37 and 27 months, respectively, while it was 46 months for patients with other cytogenetic abnormalities (p = 0.01). Accordingly, sole abnormalities of +9, del(20q) and del(13q) were categorized as being favorable (n = 35) and complex abnormalities and sole +8 as unfavorable (n = 20); the respective median survivals were 112 and 34 months (p=0.002; Figure). Multivariable analysis confirmed the IPSS-independent prognostic value of cytogenetic risk categorization and the intra-IPSS risk prognostic distinction was most apparent in the int-1 group: median survival was 35 and 81 months in the presence of unfavorable or favorable cytogenetic markers, respectively (p=0.0009; Figure). Conclusion: The current study identifies sole +9, along with del(13q) and del(20q), as favorable and sole +8, along with complex abnormalities, as unfavorable cytogenetic markers of prognosis in PMF. Cytogenetic risk categorization in PMF has an IPSS-independent prognostic value that is important in patient selection for specific therapy. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2895 Poster Board II-871 Background: Recent studies have reported a significant association between JAK2V617F acquisition and a specific JAK2 germline haplotype; rs12343867 (located at intron 14 of the JAK2 gene) is one of several SNPs that tag this haplotype. We performed rs12343867 SNP analysis in a consecutive cohort of patients with primary myelofibrosis (PMF) in order to study the clinical and laboratory correlates of the particular JAK2 haplotype and its effect on survival. Methods: Study patients were recruited form the Mayo Clinic database for PMF. Molecular studies were performed on DNA extracted from stored bone marrow. rs12343867 SNP genotyping was performed by a commercially available Taqman assay. Quantitative JAK2V617F analysis was done according to previously published methods. Standard statistical methods were used to test significance of associations between SNP genotype and other variables. Survival analysis was performed by the Kaplan-Meier method and comparisons made by the log-rank test. Cox regression model was used for multivariable analysis. Results: 132 patients with PMF were studied (median age 62, range 28-82; 82 males). Risk distribution according to the International Prognostic Scoring System (IPSS) for PMF were low in 39 (29%) patients, intermediate-1 in 41 (31%), intermediate-2 in 25 (20%) and high in 27 (20%). 77 (58%) patients were JAK2V617F positive; median mutant allele burden was 26% (range 1-85) and 21 patients displayed > 50% mutant allele burden. The rs12343867 genotype distributions were C/C 22%, C/T 44% and T/T 34% . The corresponding figures in JAK2V617F positive/negative cases were 31%/9%, 38%/53%, 31%/38% (p=0.01). Among the 21 patients with > 50% JAK2V617F allele burden, 14 (67%) displayed the C/C allele, 2 C/T and 5 T/T. The specific SNP genotype was not significantly affected by age (p=0.33), sex (p=0.46), leukocyte count (p=0.39), platelet count (p=0.09), or IPSS risk category (p=0.63). Patients were followed for a median of 54 months and during this period 73 (55%) deaths were documented. The T/T SNP genotype was significantly associated with shortened survival, compared to either C/C or C/T (p=0.001; Figure). Multivariable analysis showed this association to be independent of IPSS, JAK2V617F mutational status, age or sex. The adverse prognostic effect of the T/T genotype was also apparent when JAK2V617F negative (p=0.01) or positive (p=0.06) cases were analyzed separately. Conversely, JAK2 mutational status or allele burden did not affect survival in patients with T/T or C/C allele. Conclusion: The current study illustrates the non-random haplotype distribution of JAK2V617F in patients with PMF. More importantly, a non-JAK2 haplotype, tagged by the rs12343867 T allele, was associated with inferior survival that is not accounted for by IPSS or JAK2V617F mutational status. These findings, together with previous observations regarding shortened survival associated with low JAK2V617F allele burden, suggest the presence of molecular events in PMF that are more aggressive than JAK2V617F and not necessarily linked to the JAK2 haplotype. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2893 Poster Board II-869 Background: A specific JAK2 germline haplotype has been associated with the occurrence of JAK2V617F in myeloproliferative neoplasms (MPN). Several SNPs, including rs12343867, tag this haplotype. We performed rs12343867 SNP analysis in a consecutive cohort of patients with essential thrombocythemia (ET) in order to study the clinical and JAK2V617F allele burden correlates of the particular SNP genotype. Methods: Study patients were recruited form the Mayo Clinic database for ET. Molecular studies were performed on DNA extracted from stored bone marrow. rs12343867 SNP genotyping was performed by a commercially available Taqman assay. Quantitative JAK2V617F analysis was done according to previously published methods. Standard statistical methods were used to test significance of associations between SNP genotype and other variables. Survival analysis was performed by the Kaplan-Meier method and comparisons made by the log-rank test. Cox regression model was used for multivariable analysis. Results: 226 patients with ET were studied (median age 57, range 14-91; 145 females). Median hemoglobin, leukocyte and platelet counts at initial diagnosis were 13.8 g/dL, 9.7 × 109/L and 1000 × 109/L, respectively. 118 patients (52%) were JAK2V617F positive and among them, 90 (76%) displayed JAK2V617F allele burden of < 10% (low allele burden group) and the median (range) mutant allele burden in the remaining 28 patients (higher allele burden group) was 12% (12-68). As expected, JAK2V617F-positive cases, compared to their mutation-negative counterparts, were older (p=0.006) and displayed higher hemoglobin (p=0.0001) and leukocyte (p<0.0001) counts and lower platelet (0.03) count. The rs12343867 genotype distributions were C/C 15%, C/T 53% and T/T 33% (expected frequency in the HapMap-CEU listed control population is ∼ 6%, 46% and 48%, respectively). The corresponding figures in JAK2V617F positive/negative cases were 17%%/11%, 53%/53%, 30%/36% (p=0.29). Unlike the case with JAK2V617F mutational status, rs12343867 SNP genotype did not correlate with age (p=0.69), hemoglobin level (p=0.47), leukocyte count (p=0.25) or platelet count (p=0.33). Patients were followed for a median of 7.4 years and during this period 56 (25%) deaths were documented. rs12343867 SNP genotype did not correlate with survival (Figure). Similarly, survival did not correlate with the presence or absence of JAK2V617F. However, patients with higher JAK2V617F allele burden displayed a shorter survival with borderline significance, during multivariable analysis that included age as a covariate. Conclusion: The current study shows the JAK2 haplotype enrichment in a large series of ET patients. However, the particular phenomenon was not significantly different between JAK2V617F positive and negative cases, which suggests specific haplotype association with the disease rather than the mutation. Consistent with this contention, rs12343867 genotype did not correlate with clinical or laboratory variables that typically associate with JAK2V617F mutational status. Furthermore, unlike the case with primary myelofibrosis, rs12343867 SNP genotype did not correlate with survival, an observation that is not surprising considering the lower level of complexity in molecular pathogenesis in ET compared to PMF. Disclosures: Pardanani: TargeGen: Research Funding; Cytopia: Research Funding. Off Label Use: Data from ongoing clinical trial will be presented. Tefferi:TargeGen: Research Funding.

Abstract Among 200 patients with primary myelofibrosis, karyotype at diagnosis was abnormal in 83 (42%). To assess their individual prognostic impact, specific cytogenetic abnormalities with more than or equal to 5 informative cases were identified and the rest grouped separately as “other abnormalities.” Median survival in patients with sole +9 (n = 6), sole 20q− (n = 21), sole 13q− (n = 8), normal karyotype (n = 117), “other abnormalities” (n = 28), complex karyotype (n = 13), and sole +8 (n = 7) were “not reached,” 112, 105, 80, 46, 34, and 28 months, respectively (P = .01). Accordingly, 4 cytogenetic risk groups were considered: (1) favorable (sole +9, 20q−, or 13q−), (2) normal, (3) unfavorable (complex karyotype or sole +8), and (4) “other abnormalities.” Multivariable analysis confirmed the International Prognostic Scoring System (IPSS)–independent prognostic value of both 4-way and 2-way (ie, favorable/normal vs unfavorable/other abnormalities; IPSS-adjusted hazard ratio = 0.37; 95% confidence interval, 0.24-0.58) cytogenetic risk categorization (P < .01). The ability to prognostically dissect a specific IPSS category has major therapeutic implications.