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NCOG-10. ASSESSMENT OF SURVIVAL AND SAFETY FOLLOWING INTRATHECAL CHEMOTHERAPY VIA OMMAYA RESERVOIR FOR LEPTOMENINGEAL DISEASE
Shah, Shiv , Butterfield, Richard , Bendok, Bernard R. , Lyons, Mark , Ariete, John, Yancey, Eric, Mrugała, Maciej M.

Neuro-Oncology | December 4, 2020 | Volume: 22 | Issue: Supplement_2 | Pages: ii131-ii131

10.1093/neuonc/noaa215.549 Get It

Abstract INTRODUCTION Leptomeningeal disease (LMD) is an aggressive, late-stage complication of systemic cancers that maintains a poor prognosis with an average survival of 3-6 months. Ommaya reservoirs (OR) are an accessible alternative to serial lumbar punctures for the delivery of intrathecal chemotherapy in the treatment of LMD. However, widespread use of OR has been limited by reports of complications, limited physicians trained in their use, and the stigma of brain surgery. Here, we assess survival and complication rates for patients who received intrathecal chemotherapy through OR for LMD treatment. METHODS After IRB approval, chart review of patients who received at least one administration of intrathecal chemotherapy through OR for LMD treatment between 2017- 2020 at Mayo Clinic in Phoenix, Arizona was conducted. Charts were reviewed for demographics, treatment type, complications, and outcomes. RESULTS A total of 10 patients were included. The median overall survival from date of first OR injection was 110.5 days (95% CI: 64 – not estimable). The median time to progression from the first injection was 55.5 days (95% CI: 45 – 753). A total of 82 OR injections were conducted for an average of approximately 8 injections per patient. Two patients (20%) experienced mild adverse events – grade 2 or lower by Common Terminology Criteria for Adverse Events with a single injection. The majority of injections involved no adverse events with the overall risk of any complication at 2.4%. None of the patients experienced infection, a commonly reported complication of OR use. CONCLUSIONS Our results support the inclusion of intrathecal chemotherapy via OR into the treatment paradigm in patients with leptomeningeal malignancies. This approach is feasible, safe, and median survival is comparable with data reported in published series. The overall complication rate in patients receiving intrathecal chemotherapy through OR is very low including the risk of infection.
616 A novel non-covalent linker peptide with nanomolar affinity for clinical IgG1 antibodies preserves antibody-antigen affinity and drug potency against PDL1+ melanoma when conjugated with DM1
Butterfield, John T. , Sutor, Shari L., Nevala, Wendy N., Markovic, Svetomir, Markovic, Svetomir N.

Regular and young investigator award abstracts | November 9, 2020 | Volume: No volume available | Issue: No issue available | Pages: A370-A371

10.1136/jitc-2020-sitc2020.0616 Get It

Improving the Definition of Response Assessment: Prognostic Value of Minimal Residual Disease Combined with PET/CT at Day 100 Post Autologous Stem Cell Transplantation in Multiple Myeloma
González-Vélez, Miguel , Arribas, Mariano , Butterfield, Richard , Mountjoy, Luke , Larsen, Jeremy T. , Reeder, Craig B. , Stewart, A. Keith, Kosiorek, Heidi , Guerrero, Carlo , Bergsagel, P. Leif , Fonseca, Rafaël

Blood | November 4, 2020 | Volume: 136 | Issue: Supplement 1 | Pages: 33-34

10.1182/blood-2020-142845 Get It

Introduction: Response assessment at day 100 post Autologous Stem Cell Transplant (ASCT) is associated with long-term relapsed free survival (RFS) and overall survival (OS) in multiple myeloma (MM). The International Myeloma Working Group (IMWG) are the preferred criteria to define best response to treatment and define relapse. In the last years, response assessment has incorporated minimal residual disease (MRD) status -associated with improved RFS and OS (Munshi et al); and PET/CT combined with clinical characteristics -also associated with favorable outcomes (Zamagni et al. NCT01910987; MMY3033). The 2016 IMWG MRD criteria, combined imaging (PET/CT) plus next-generation sequencing (NGS) MRD-negative to define complete response (CR). To our knowledge, there is limited data examining the correlation and prognostic value of MRD and FDG-PET/CT at day 100 post ASCT in MM. IN this study, we aimed to determine the prognostic valued of MRD by NGS combined with PET/CT in RFS and OS status after high dose chemotherapy and ASCT in MM. Methods: Patients who underwent ASCT for MM at Mayo Clinic Arizona and had MRD and PET/CT data were included in the study. Clinical data was obtained via retrospective chart review. Cytogenetic risk (CyR) was classified using the mSMART criteria . Disease and ASCT related characteristics were compared by MRD status. MRD was measured by NGS on bone marrow aspirates using the previosly validated clonoSEQ ® Assay (Adaptive Biotechnologies Corporation, Seattle, USA) tracking the IgH, IgK and IgL rearrangements at a minimum sensitivity level of 10-5. MRD was defined by residual clonal cells per million nucleated cells as: negative= 0, borderline= 1-5, positive >5. PET/CT scans were performed locally at baseline and at day 100. Comparisons were performed using the chi-square test for categorical variables, Wilcoxon rank-sum test for continuos variables, McNemar's test and Cohens's Kappa for agreement measures. Results: A total of 103 patients had matched MRD and PET/CT assessment around day 100 (+/-9 days) and were included in the analysis. Median age at diagnosis was 62 years (range, 54-66 years), 71 patients (68.9%) were men. CyR was standard risk in 49 (47.6%), high-risk in 39 (37.9%) and unknown in 15 (14.6%) patients. Most 75 (72.8%) patients were MRD positive, 16 (15.5%) were MRD negative, and 12 (11.7%) borderline. The median main MRD clone detected was 64 (range 0-91,874). 70 patients (68%) and 33 (32%) had a negative and positive PET/CT respectively. The median follow-up time was 18 months (range, 13-31 months). At the time of data analysis, 10 patients (9.7%) had relapsed and only 4 (3.9%) had died. There was a high-correlation between MRD status and PET/CT, 31 patients (93.9%) with positive PET/CT were also MRD positive (p=0.0027). There were no statistical differences between PET/CT and CyR (p=0.95). We analyzed the correlation using the FREQ procedure (McNemars's test); there was a strong association between positive PET/CT and positive MRD in 31/33 patients (93.9%, high sensitivity), and low association for negative PET/CT the negative/borderline MRD in 26/70 (37.1%, low specificity; p<0.001). The agreement measure between the PET/CT and MRD using negative/borderline combined had a kappa of 0.23 (95% CI 0.11, 0.35) indicating a fair agreement beyond chance (Figure 1). PET/CT-CT was a statistically significant predictor of worse RFS (HR 3.53, 95%CI: 1.02-12.24, p<0.0337) and OS (HR 11.38, 95%CI: 1.18-109.56, p<0.0078) (Figure 2-3, respectively). MRD was not predictive of neither RFS (HR 1.72, 95%CI: 0.36-8.14, p<0.49) or OS (p<0.16). Conclusions: In conclusion, we demonstrate that the combination of MRD by NGS (clonoSEQ ®) and PET/CT at day 100 are complementary and have a high sensitivity (true positive rate) and fair correlation of agreement but low specificity (true negative rate). PET/CT was the best most sensitive technique to prognosticate RFS and OS. We did not find prognostic correlation of MRD with RFS and OS. However, our findings might be confounded by the low risk of relapse and death, a longer follow-up may demonstrate clinically important differences. Our results add evidence that MRD plus PET/CT improve the definition of CR in MM patients post ASCT. Prospective studies are needed to elucidate the optimal timing and role of combined MRD, PET/CT with other prognostic markers of clinical outcomes. Disclosures Larsen: Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen Oncology: Honoraria, Membership on an entity's Board of Directors or advisory committees. Fonseca:Juno: Consultancy; Kite: Consultancy; Aduro: Consultancy; OncoTracker: Consultancy, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy; Bayer: Consultancy; Janssen: Consultancy; Takeda: Consultancy; Novartis: Consultancy; Pharmacyclics: Consultancy; Sanofi: Consultancy; Oncopeptides: Consultancy; GSK: Consultancy; AbbVie: Consultancy; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy; BMS: Consultancy; Celgene: Consultancy.
Five Year Prevalence of Pelvic Organ Prolapse After Vaginal Hysterectomy with Prophylactic Apical Support
Talbott, Jennifer , Yi, Johnny , Butterfield, Richard , Wasson, Megan , Talbott, Jennifer M V , Wasson, Megan

Journal of Gynecologic Surgery | October 19, 2020 | Volume: 37 | Issue: 2 | Pages: 127-131

10.1089/gyn.2020.0104 Get It

Migraine Treatment in Pregnancy: An American Headache Society Survey
Hamilton, Katherine , Singh, Rashmi B. Halker , Ailani, Jessica , Butterfield, Richard , Robbins, Matthew S. , Hamilton, Katherine T , Halker Singh, Rashmi B , Butterfield, Richard J , Robbins, Matthew S , Ailani, Jessica

Headache: The Journal of Head and Face Pain | September 29, 2020 | Volume: 60 | Issue: 10 | Pages: 2594-2596

10.1111/head.13974 | PMID 32990322 Get It

Current Practices for Screening and Management of Financial Distress at NCCN Member Institutions
Khera, Nandita , Sugalski, Jessica , Krause, Diana, Butterfield, Richard , Zhang, Nan , Stewart, F. Marc, Carlson, Robert W. , Zafar, S. Yousuf , Lee, Stephanie J. , Griffin, Joan M. , Lee, Stephanie J

Journal of the National Comprehensive Cancer Network | July 7, 2020 | Volume: 18 | Issue: 7 | Pages: 825-831

10.6004/jnccn.2020.7538 | PMID 32634772 Get It

Background: Financial distress from medical treatment is an increasing concern. Healthcare organizations may have different levels of organizational commitment, existing programs, and expected outcomes of screening and management of patient financial distress. Patients and Methods: In November 2018, representatives from 17 (63%) of the 27 existing NCCN Member Institutions completed an online survey. The survey focused on screening and management practices for patient financial distress, perceived barriers in implementation, and leadership attitudes about such practices. Due to the lack of a validated questionnaire in this area, survey questions were generated after a comprehensive literature search and discussions among the study team, including NCCN Best Practices Committee representatives. Results: Responses showed that 76% of centers routinely screened for financial distress, mostly with social worker assessment (94%), and that 56% screened patients multiple times. All centers offered programs to help with drug costs, meal or gas vouchers, and payment plans. Charity care was provided by 100% of the large centers (≥10,000 unique annual patients) but none of the small centers that responded (<10,000 unique annual patients; P =.008). Metrics to evaluate the impact of financial advocacy services included number of patients assisted, bad debt/charity write-offs, or patient satisfaction surveys. The effectiveness of institutional practices for screening and management of financial distress was reported as poor/very poor by 6% of respondents. Inadequate staffing and resources, limited budget, and lack of reimbursement were potential barriers in the provision of these services. A total of 94% agreed with the need for better integration of financial advocacy into oncology practice. Conclusions: Three-fourths of NCCN Member Institutions reported screening and management programs for financial distress, although the actual practices and range of services vary. Information from this study can help centers benchmark their performance relative to similar programs and identify best practices in this area.
Exogenous Infusion of Epinephrine Augments Cardiac Output during Simulated Hemorrhage in Humans
Butterfield, Brian P., Shepherd, John R.A. , Butterfield, Brian P., Senefeld, Jonathon W. , Wiggins, Chad C. , Joyner, Michael J. , Curry, Timothy B. , Convertino, Víctor A. , Baker, Sarah E.

The FASEB Journal | April 19, 2020 | Volume: 34 | Issue: S1 | Pages: 1-1

10.1096/fasebj.2020.34.s1.09376 Get It

Background Lower body negative pressure (LBNP) simulates hemorrhage, evoking compensatory cardiovascular mechanisms of increased heart rate (HR) while stroke volume (SV) and cardiac output (CO) progressively decline, ultimately leading to presyncope. Previous work has shown that circulating levels of plasma epinephrine are elevated during LBNP; however, the role of early administration of epinephrine in compensatory cardiovascular mechanisms to simulated hemorrhage is not well understood. Purpose We hypothesized that during simulated hemorrhage, a low‐dose exogenous infusion of epinephrine in humans would: 1) augment HR response, 2) attenuate the decline of SV and CO, and 3) prolong time to tolerance. Methods Nine healthy subjects (5M/4F, 35±9yrs, BMI 25±1 kg·m −2 ) participated in LBNP on two separate study days. Protocols on each day consisted of a 10‐minute pre‐infusion baseline, 15‐minute infusion period (randomized to saline or epinephrine, dose = 0.1 μg·kg −1 ·min −1 , delivered through a peripherally inserted central catheter), 10‐minute post‐infusion baseline, and 5 minute stages of progressive LBNP with stepwise increases of 10–15 mmHg negative pressure until tolerance (systolic blood pressure less than 80 mmHg, bradycardia, or voluntary termination due to presyncopal symptoms). Heart rate (HR; electrocardiogram) and blood pressure (BP; radial arterial catheter) were recorded continuously. Cardiovascular function (HR, SV, CO, and systemic vascular resistance (SVR)) was determined using arterial waveform analysis. Data were analyzed via percent tolerance using repeated measures ANOVA with student method for pairwise comparisons. Results Infusion of exogenous epinephrine lowered MAP (p<0.01) and diastolic blood pressure (DBP; p<0.001), but raised systolic blood pressure (SBP; p=0.019) throughout all stages of LBNP. Epinephrine compared to saline augmented mean HR, SV and CO to the penultimate stage of LBNP (p≤0.01 for all cardiac measures) and concurrently reduced SVR (p=0.002). However, time to tolerance was not significantly different between epinephrine and saline conditions (1415 ± 79 vs. 1475 ± 150s, respectively; p=0.69). Discussion Our findings suggest that during simulated hemorrhage exogenous epinephrine can augment cardiac function without increasing tolerance to progressive central hypovolemia. During the epinephrine infusion, benefits to cardiac function may have been limited by reduced vascular resistance. Support or Funding Information The United States Department of Defense W81XWH‐13‐2‐0038
Low Incidence of FIP1L1-PDGFRA in Eosinophilic Patients and Long-Term Experience with Imatinib Therapy.
Pardanani, Animesh , Li, Chin‐Yang, Wolanskyj, Alexandra P., Elliott, Michelle A. , Camoriano, John , Butterfield, Joseph H. , Dewald, Gordon W., Tefferi, Ayalew , Ketterling, Rhett P.

Blood | April 19, 2020 | Volume: 106 | Issue: 11 | Pages: 2590-2590

10.1182/blood.v106.11.2590.2590 Get It

Abstract Background: The FIP1L1-PDGFRA fusion, an imatinib-sensitive molecular target, is detected in a subset of cases with moderate-to-severe eosinophilia (eosinophil count ≥1500/μL). Using 2 FISH strategies to detect loss of the CHIC2 locus as a surrogate marker of the FIP1L1-PDGFRA fusion, we previously found 14% of cases to be CHIC2-deleted when studying bone marrow smears from 81 adult patients with moderate-to-severe, non-reactive eosinophilia at our institution (Blood 2004, 104:3038–3045). Since then, the FISH test has been made available for routine clinical use both within our institution, and to external physicians as a mail-in test, for the workup of patients with eosinophilic disorders, including systemic mast cell disease (SMCD). Study design: FISH data, subsequent to the test’s introduction into routine clinical practice (from Nov. 2003), were retrospectively analyzed for CHIC2-deletion. Data from the initial pilot study of 81 patients was not used in this analysis (Table). The imatinib treatment analysis, however, included all CHIC2-deleted patients treated at our institution, including those from the pilot study (Table). Results: A total of 741 patients were studied in the post-pilot phase. Of these, 20 cases were found to be CHIC2-deleted, with an overall prevalence of 2.7% (Table). Of the 219 patients seen at our institution, 13 (all male) were found to be CHIC2-deleted (Table) (prevalence=5.9%), and of these, 10 have been treated with imatinib (100 mg/day starting dose) to date. Nine patients are evaluable for response - all achieved a complete clinical and histological remission (7 patients were tested by FISH post-treatment - all achieved cytogenetic remission). One patient received concomitant corticosteroids for co-morbidities and could not be evaluated for response. After a median follow-up of 24 months (range 17 to 39 months), all 9 patients continue to be in remission, with a normal eosinophil count. At last follow-up, one patient had discontinued imatinib and the others were on maintenance therapy at the following dose: 100mg/wk (n=1), 100mg BIW (n=1), 100mg TIW (n=2), 50mg QOD (n=1), and 100 mg/day (n=3). Conclusions: FIP1L1-PDGFRA prevalence in non-selected patients with eosinophilia is lower than anticipated from prior studies. Patients with FIP1L1-PDGFRA exhibit durable responses to imatinib therapy. It may be feasible to maintain some patients in remission on an empirically derived, intermittent schedule of low-dose imatinib. Pilot Data Post-pilot Data (n=741) Total Mayo samples Mayo samples Mail-in samples Number of Patients 81 138 603 822 Number CHIC2-deleted 11 2 18 31 Prevalence 14% 1.4% 3.0% 3.8% Number Imatinib treated 8 2 n/a 10
Cytoreductive Therapy in Systemic Mastocytosis: Outcome Analysis and Response Prediction in 134 Consecutive Patients.
Pardanani, Animesh , Butterfield, Joseph H. , Li, Chin Yang, Tefferi, Ayalew , Lim, Ken‐Hong , Li, Chin‐Yang

Blood | April 18, 2020 | Volume: 112 | Issue: 11 | Pages: 1759-1759

10.1182/blood.v112.11.1759.1759 Get It

Abstract Background: Current therapy in adult systemic mastocytosis (SM) includes observation alone, topical therapy for cutaneous disease, symptomatic non-cytoreductive therapy and cytoreductive therapy. The latter involves several drugs whose individual merit in the treatment of SM has not been well characterized. Patients and Methods: Diagnosis of SM was according to the 2001 WHO criteria (World Health Organization Classification of Tumours of Hematopoietic and Lymphoid Tissues, p 1–351. Lyon, France: IARC Press; 2001). Response to cytoreductive therapy was assessed by consensus criteria (Eur J Clin Invest.2007;37:435). The study population was selected from a series of 342 adult SM patients referred to our institution and seen between 1964 and 2008. KITD816V mutation analysis was performed by DNA sequencing. Results: A total of 134 study patients received treatment that included at least one cytoreductive drug as either first-line (n=105) or second-line (n=29) therapy. Interferon-alpha with or without prednisone (n=58), hydroxyurea (n=43), imatinib mesylate (n=42) and 2-chlorodeoxyadenosine (n=26) were the most frequently used cytoreductive agents accounting for 120 of the 134 study cases; the remaining 14 patients received other cytoreductive drugs, none of which were effective. i. Interferon-alfa (IFN-a) with or without prednisone IFN-a with or without prednisone (24 and 34 patients, respectively) was given to 12 patients with indolent SM (ISM), 14 aggressive SM (ASM), and 32 SM with associated clonal hematological non-mast cell lineage disease (SM-AHNMD). For all 58 patients receiving therapy, complete (CR), major (MR), and partial (PR) response/regression were achieved in 3, 7, and 14 patients, respectively, for an overall response rate (ORR) of 41%. ORR in ISM, ASM, and SM-AHNMD was 50%, 43%, and 38%, respectively. Median duration of response was 12 months (range, 1–117 months). Anemia and elevated ESR were significantly associated with inferior ORR; 29% vs. 56% (p=0.04) and 14% vs. 57% (p=0.01), respectively. BM detection of KITD816V did not appear to affect response rates (p=0.4). ii. Hydroxyurea (HU) HU was given to 2 ASM, 40 SM-AHNMD and 1 mast cell leukemia (MCL) patients. The drug was used as first-line therapy in 30 patients. MR and PR were achieved in 1 and 8 SM-AHNMD patients, respectively (ORR=21%). Median duration of response was 37 months (range, 5–84 months). iii. Imatinib mesylate (IM) in patients with SM and associated eosinophilia IM was given to 22 SM patients who had associated eosinophilia (SM-eos): 2 had ISM, 2 ASM, and 18 SM-AHNMD. The drug was used as first-line therapy in 9 patients. Ten of the 22 patients with SM-eos were known to harbor the FIP1L1-PDGFRA fusion mutation and all responded to IM (ORR=100%). None of 5 FIP1L1-PDGFRA-negative SM-eos patients had a response to IM. In the remaining 7 patients with unknown mutation status, 4 patients had a response to IM (1 CR, 1 MR, and 2 PR). iv. IM in patients with SM not associated with eosinophilia IM was administered to 20 SM patients without associated eosinophilia (7 ISM, 2 ASM, 10 SM-AHNMD, and 1 MCL). Response was documented in 4 (20%) patients (1 CR, 1 MR, and 2 PR) including 1 with ISM, 2 with ASM and 1 with SM-AHNMD. Median duration of response was 19.5 months (range, 9–69 months). Two patients developed interstitial pneumonitis. v. 2-Chlorodeoxyadenosine (2-CdA) 2-CdA was given to 10 ISM, 3 ASM, and 13 SM-AHNMD patients; the drug was used as first-line therapy in 8 patients. CR, MR and PR were achieved in 1, 7, and 4 patients, respectively (ORR=46%). ORR in ISM, ASM, and SM-AHNMD was 50%, 33%, and 46%, respectively. Median duration of response was 11 months (range, 3–74 months). Presence of leukocytosis (WBC &gt; 10 x 109/L), monocytosis (absolute monocyte count &gt; 0.9 x 109/L) or circulating immature myeloid cells was significantly associated with inferior response; 13% vs. 61% (p=0.02); 11% vs. 69% (p=0.006) and 0% vs. 71%, (p=0.001), respectively. Response was not affected by BM detection of KITD816V (p=1.0). Conclusions: Both IFN-a and 2-CdA are reasonable treatment options, with comparable efficacy, for symptomatic SM including the subcategories of ISM, ASM and SM-AHNMD. IFN-a response was significantly better in the absence of anemia or elevated ESR. 2-CdA response was similarly better in the absence of leukocytosis, monocytosis or circulating immature myeloid cells. The therapeutic value of IM was limited to FIP1L1-PDGFRA-positive disease.
TG101348, An Orally Bioavailable JAK2-Selective Inhibitor, Potently Inhibits KITD816V and FIP1L1-PDGFRA in Vitro
Kittur, Jaya, Butterfield, Joseph H. , Shorr, Jolene, Tefferi, Ayalew , Pardanani, Animesh , Lasho, Terra L.

Blood | April 18, 2020 | Volume: 112 | Issue: 11 | Pages: 2807-2807

10.1182/blood.v112.11.2807.2807 Get It

Abstract Background: Systemic mastocytosis (SM) and hypereosinophilic syndrome (HES) are JAK2V617F-negative orphan diseases without effective long-term therapeutic options. Both of these diseases share clinical and laboratory features with FIP1L1-PDGFRA-positive chronic eosinophilic leukemia (CEL). SM is associated with KITD816V or other KIT mutations. HES is currently not molecularly characterized. The exquisite sensitivity of FIP1L1-PDGFRA to inhibition by imatinib mesylate (IM) underlies the efficacy of this agent in treating FIP1L1-PDGFRA-positive CEL. In contrast, KITD816V is resistant to inhibition by IM, and is only moderately sensitive to dasatinib (cellular IC50=micromolar concentrations), which may explain the relatively disappointing clinical responses in SM with these agents. TG101348 is an orally bioavailable JAK2-selective inhibitor that is currently being tested in a Phase 1 clinical trial for the treatment of myelofibrosis. The aim of the current study was to evaluate TG101348 (relative to the tyrosine kinase inhibitors IM, dasatinib, and sorafenib) for its ability to: inhibit growth of leukemic cell lines that carry KITD816V and FIP1L1-PDGFRA; and inhibit the in vitro growth of eosinophil colonies derived from progenitor cells from HES patients. Methods: The following cell lines were used for in vitro experiments: HMC-1, a mast cell leukemia line (KITD816V-positive); EOL-1, a CEL derived line (FIP1L1-PDFRA-positive), Ba/F3 T674I, a Ba/F3 line that express the IM-resistant FIP1L1-PDFRAT674I mutation, and HEL, a human erythroleukemia line (JAK2V617F-positive). Cell proliferation assays were performed in triplicate using the XTT assay (Leukemia. 2007 21:1658). Drug concentrations in these experiments ranged from 2.9 × 10−12 M to 10−4 M. JAK Inhibitor I (Calbiochem) is a non-selective JAK inhibitor tool compound. Eosinophil colonies were obtained by plating PBMCs from healthy controls or HES patients in methylcellulose, in the presence of IL-3, IL-5, and GM-CSF. Effects of IM and TG101348 on eosinophil colony growth were studied in parallel experiments. Results: Consistent with prior observations, the HMC-1 cell line was resistant to inhibition by IM (IC50&gt;10 mM), but was moderately sensitive to dasatinib (Table). In contrast, TG101348 inhibited HMC-1 growth at nanomolar concentrations, similar to its effect on HEL cells that harbor the JAK2V617F mutation. TG101348 inhibited HMC-1 growth 53-fold and 4-fold more potently than IM and dasatinib, respectively (Figure). Sorafenib, a multikinase inhibitor that reportedly has activity against KIT kinase (enzyme IC50=68 nM), had only a limited effect on HMC-1 growth (IC50=4000 nM). In contrast to HMC-1, EOL-1 growth was inhibited by IM, dasatinib, sorafenib, and TG101348 at picomolar concentrations (Table). The T674I mutation (in the context of FIP1L1-PDGFRA) corresponds to the T315I mutation in BCR-ABL – it occurs infrequently in CEL and is usually found in the context of transformation to acute leukemia. Growth of Ba/F3 cells harboring FIP1L1-PDFGRA-T674I has been shown to be inhibited by sorafenib (confirmed in this report; Table) and nilotinib, at nanomolar concentrations. TG101348 is less potent at inhibiting growth of these cells, with cellular IC50 of ~2 mM – pharmacokinetic data from the ongoing Phase I study of TG101348 shows that this concentration is achievable in plasma with once daily dosing. Drug Cellular IC50 HMC-1 (nM) EOL-1 (pM) Ba/F3 T674I (nM) HEL (nM) Imatinib 18800 4 10700 - Dasatinib 1300 &lt;1 30900 - Sorafenib 4000 2 16 - Jak Inhibitor I 926 30 4300 ? TG101348 355 &lt;1 1950 300 Figure Figure Conclusions: The JAK2-selective inhibitor TG101348 is a potent inhibitor of KITD816V and FIP1L1-PDGFRA, warranting clinical trials using this drug in SM and FIP1L1- PDGFRA-positive CEL. Data regarding TG101348 effects on signaling intermediates in leukemic cell lines and on eosinophil colony growth will be presented at the meeting – data from the latter experiments may indicate a therapeutic role for TG10134 in the treatment of patients with HES.