Page 68 - Haematologica-5

M. Schneeweiss et al.
internal organs, including the bone marrow.1-3 Various types of SM have been recognized by the World Health Organization (WHO).8-11 The indolent variant of SM is associated with ‘hematologic stability’ and thus with an almost normal life expectancy.12-14 By contrast, the progno- sis in patients with advanced SM, including SM with an associated hematologic neoplasm (AHN), aggressive SM (ASM) and MC leukemia (MCL) is unfavorable, with short survival times and poor responses to conventional therapy.1-5,12,13,15 Current research is, therefore, focusing on therapeutic targets and the effects of novel antineoplastic drugs on various cell types relevant to advanced SM.16 Since most patients with SM also suffer from mediator- related symptoms that may sometimes be severe or even life-threatening, such drugs are often selected based on their dual effects on MC growth and MC activation.
Most patients with SM express the D816V-mutated vari- ant of the stem cell factor receptor, KIT, which mediates ligand-independent activation and autonomous growth and differentiation of MC.17-22 The D816V KIT point muta- tion also confers resistance against several tyrosine kinase inhibitors, including imatinib.23-26 Novel kinase blockers act- ing on KIT D816V have, therefore, been developed. The highlighting example is midostaurin (PKC412).27,28 However, despite superior clinical efficacy seen in a global phase II trial,28 patients with advanced SM often exhibit or acquire resistance.28,29 A number of different mechanisms may underlie resistance against midostaurin. One obvious problem is that the drug does not suppress all clinically rel- evant sub-clones and cell-types, especially cells lacking KIT D816V.28,29 Such sub-clones are often seen in the context of advanced SM. Over 50% of these patients have or develop an AHN.30-32 Of these patients with an AHN, approximate- ly 80-90% have an associated myeloid neoplasm, the most frequent ones being chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia (AML).8-11,30-32 In these patients, leukemic expansion of monocytes and/or blast cells is typically found. In other patients, an expansion of eosinophils, sometimes resembling chronic eosinophilic leukemia (SM-CEL), is found. In most of these patients,
eosinophils display KIT D816V.33 By contrast, expression of rearranged PDGFR variants is rarely seen in SM, although in some patients with a FIP1L1/PDGFRA fusion gene, the MC expansion has a histopathological picture indistin- guishable from that of SM.34 Treatment of SM-AHN repre- sents a clinical challenge because the AHN-component is often resistant.16,32
DCC-2618 is a switch-control type II inhibitor of KIT, which arrests KIT in an inactive state, regardless of activat- ing mutations, such as KIT D816V.35 Moreover, several additional oncogenic kinases, including FLT-3, PDGFRA, PDGFRB, KDR, TIE2 and FMS are recognized by DCC- 2618.35 Recently, the first clinical trials with DCC-2618 (NCT02571036) were started in patients with kinase-dri- ven malignancies. In addition, first preclinical studies have shown that DCC-2618 may exert antineoplastic effects on neoplastic MC.36
In our current study, we show that DCC-2618 is a potent inhibitor of growth and survival of neoplastic human MC expressing various KIT mutations. Furthermore, we show that DCC-2618 produces growth inhibition and apoptosis in other cell types that play a role in advanced SM. Finally, we show that DCC-2618 inhibits IgE-dependent histamine secretion from basophils and tryptase secretion from MC. All in all, our data suggest that DCC-2618 is a promising, novel drug for the treatment of advanced SM.
Methods
Reagents
The reagents used in this study are described in the Online Supplement. DCC-2618 and its active metabolite, DP-5439, were kindly provided by Dr. B. Smith (Deciphera Pharmaceuticals LLC, Lawrence, KS, USA).
Isolation of primary neoplastic cells
Primary neoplastic cells were isolated from bone marrow samples of 11 patients with SM. The bone marrow cells were obtained during routine diagnostic investigations after written
Table 1. Characteristics of patients with systemic mastocytosis and response of neoplastic cells to DCC-2618 and DP-5439.
Patient n.
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
#11
DCC-2618 DP-5439 PKC412 IC50 IC50 IC50
114nM 414nM 56nM
390 nM 35 nM 554nM n.a. 1481nM n.a. 1584nM n.a. 366nM n.a.
90 m
63 m
65 m
78 m
91 m MCL + 330 20 50 321nM 592nM 65nM
Age m/f Diagnosis, SM KIT Serum tryptase BM MC % MC variant D816V ng/mL infiltration % in MNC
68 m ISM + 83.3 n.a. 1
56m ISM + 103 49 f ISM - 22.9 66 m ISM-MPN-eo + 170 82 f SSM + 284 57 f ASM + 87.9
20 5 10 n.a. 5 n.a.
240 nM 198nM 394nM 347nM 331nM 386nM 393nM 460nM
ASM + 125 ASM-AML + 33.9 ASM-CMML + 220 ASM-MPN-eo + 45.9
50 50 20 15 50 15
n.a. n.a. 25 8 30
679nM 360nM 554nM 66nM 907nM n.a.
5 83nM 64nM 114nM
800
Diagnoses were established according to WHO criteria. Primary bone marrow cells were incubated with various concentrations of DCC-2618, DP-5439 or midostaurin (PKC412) at37°Cfor48h.Proliferationwasthendeterminedbymeasuringuptakeof3H-thymidineandIC50 valueswerecalculated.WHO:WorldHealthOrganization;m:male;f:female; SM: systemic mastocytosis; PB, peripheral blood; BM, bone marrow; MC: mast cells; MNC, mononuclear cells, nM, nanomolar; n.a., not available; IC50, half maximal inhibitory con- centration; ISM: indolent SM; MPN: myeloproliferative neoplasms; SSM: smoldering SM; ASM: aggressive SM; CMML: chronic monomyelocytic leukemia; MCL: mast cell leukemia.
haematologica | 2018; 103(5)