KIT Gene Research Articles

Systemic mastocytosis mimicking blastic plasmacytoid dendritic cell neoplasm: a case report

BackgroundSystemic mastocytosis (SM), a rare myeloid neoplasm, is defined as a clonal and neoplastic proliferation of mast cells in at least one extracutaneous organ(s). The pathologic diagnosis and treatment of SM are challenging.Case presentationWe presented a 44-year-old male patient who had endured abdomen discomfort for 4 years and diarrhea for 5 months. Colonoscopy and PET/CT found a protuberant lesion in the cecum with adjacent lymphadenopathy. Histopathology of the cecum biopsy showed diffuse infiltration of medium-sized round/oval cells in lamina propria with immunohistochemical expressions of CD45, CD117, CD25, CD68, CD123, CD56, CD4, and CD35, mimicking blastic plasmacytoid dendritic cell neoplasm. Sanger sequencing revealed missense mutation (D816V) in the exon 17 of KIT gene. Serum tryptase level was 38.56 ng/ml. No abnormality was found in skin examination and bone marrow biopsy. No primitive cells were observed in bone marrow smear and peripheral blood smear. The diagnosis of aggressive SM with intestinal tract involvement was established. The patient received avapritinib treatment at an initial dosage of 200 mg once daily and exhibited dramatic clinical improvement but memory impairment within 1 month. No recurrence was observed in 1-year follow-up at the adjusted avapritinib dose (75 mg once daily).ConclusionsSM is very rare and should be considered in patients with long-term diarrhea symptoms and hematopoietic/lymphoid-appearing tumors. KIT D816V mutation contributes to the differentiation of CD123, CD4, and CD56 immunoreactive SM from blastic plasmacytoid dendritic cell neoplasm. The rare side-effect of memory impairment in this case helps to accumulate the experience of avapritinib in treating KIT D816V-mutant SM.

Evaluation of RT-PCR assays for detection of SARS-CoV-2 variants of concern

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) pandemic has been considered with great importance on correct screening procedure. The detection efficiency of recent variants of concern were observed by comparing 5 commercial RT-PCR kits and a SYBR-green method developed and validated in our laboratory. The RNA was extracted from nasopharyngeal samples from suspected COVID-19 patients and RT-PCR assay was performed according to the instruction of the respective manufacturers. The specificity and sensitivity of Maccura kit was 81.8% and 82.5%, A*Star kit was 100% and 75.4%, Da An Gene kit was 100% and 68.4%, Sansure kit was 54.5% and 91.2% and TaqPath kit was 100% and 70.2% respectively. Our in house SYBR-Green method showed a consistent detection result with 90.9% specificity and 91.2% sensitivity. We also found that detection kits targeting more genes showed better accuracy which facilitates less false positive results (< 20%). Our study found a significant difference (p < 0.005) in Ct value reported for common target genes shared by the RT-PCR kits in relation with different variants of COVID-19 infection. Recent variants of concerns contain more than 30 mutations in the spike proteins including 2 deletion and a unique insertion mutation by which makes detection of these variants difficult and these facilitates the variants to escape from being detected.

Identification of M4205─A Highly Selective Inhibitor of KIT Mutations for Treatment of Unresectable Metastatic or Recurrent Gastrointestinal Stromal Tumors.

The treatment of gastrointestinal stromal tumors (GISTs) driven by activating mutations in the KIT gene is a prime example of targeted therapy for treatment of cancer. The approval of the tyrosine kinase inhibitor imatinib has significantly improved patient survival, but emerging resistance under treatment and relapse is observed. Several additional KIT inhibitors have been approved; still, there is a high unmet need for KIT inhibitors with high selectivity and broad coverage of all clinically relevant KIT mutants. An imidazopyridine hit featuring excellent kinase selectivity was identified in a high-throughput screen (HTS) and optimized to the clinical candidate M4205 (IDRX-42). This molecule has a superior profile compared to approved drugs, suggesting a best-in-class potential for recurrent and metastatic GISTs driven by KIT mutations.

Phase 1/1b first-in-human study of IDRX-42, a novel oral tyrosine kinase inhibitor (TKI), in patients with metastatic and/or unresectable gastrointestinal stromal tumors (GISTs).

TPS483 Background: The majority of GISTs are driven by constitutively activated kinases, either KIT or platelet-derived growth factor-alpha ( PDGFRA), and respond to TKI treatment (eg, imatinib, sunitinib, regorafenib, ripretinib). Most GISTs develop heterogeneous resistance to TKI during treatment, usually driven by secondary mutations in the primary kinase oncogene ( KIT or PDGFRA). Novel therapies are needed to prevent emergence of resistant subclones or to treat TKI-resistant GISTs. IDRX-42 (formerly M4205) is a potent, highly selective, orally administered small-molecule TKI targeting disease-specific oncogenic drivers and a range of clinically relevant resistance mutations of KIT. Nonclinical studies of IDRX-42 have demonstrated robust antitumor activity in patient and cell line-derived GIST xenograft models, including models with relevant KIT mutations and TKI resistance mutations (De Sutter et al AACR 2022). Methods: IDRX-42-001 is a phase 1/1b, first-in-human, open-label, multicenter study to evaluate single-agent IDRX-42 in participants with metastatic and/or surgically unresectable GISTs. Phase 1 dose escalation utilizes a 3+3 design to evaluate safety, tolerability, PK, and preliminary antitumor activity of IDRX-42 to establish the MTD and RP2D. Phase 1b will consist of exploratory cohorts with selected lines of prior therapy to assess the antitumor activity of IDRX-42 and further characterize its safety profile at RP2D. Eligible participants are ≥18 yr old with ECOG PS 0–1, documented pathogenic mutation in KIT or any PDGFRA mutation other than exon 18 mutations, and ≥1 measurable lesion per mRECIST v1.1 by investigator assessment. Phase 1 dose-escalation participants must have documented progression on at least imatinib. For phase 1b exploratory cohorts, cohort 1 participants must have progressed on imatinib only (2nd line); cohort 2 participants must have progressed on imatinib and sunitinib (3rd line) or progressed on imatinib, sunitinib, and an additional agent (ie, regorafenib or ripretinib; 4th line); cohort 3 participants must have progressed on imatinib, sunitinib, regorafenib, and ripretinib (≥5th line). IDRX-42 will be initiated at 120 mg PO QD in 28-d cycles until disease progression, unacceptable toxicity, or other reason. Primary endpoints are to determine the nature, incidence, &amp; severity of IDRX-42 TEAEs and DLTs (phase 1), and to evaluate safety and determine ORR per investigator assessed mRECIST v1.1 (phase 1b). Secondary efficacy endpoints include PK parameters, DoR, PFS, and time to response related to IDRX-42. Exploratory endpoints will evaluate potential predictive and pharmacodynamic markers using ctDNA, as well as changes in KIT, PDGFRA, and other relevant gene mutant allele fractions and their correlation with clinical outcomes. Enrollment is ongoing (NCT05489237). Clinical trial information: NCT05489237 .

Primary Hepatic Extra-gastrointestinal Stromal Tumors: Molecular Pathogenesis, Immunohistopathology, and Treatment.

Gastrointestinal stromal tumors are the most common mesenchymal tumors of the gastrointestinal tract. They originate from the interstitial cells of Cajal and are usually found in extrahepatic gastrointestinal sites. However, a small subset are derived from the liver and are known as primary hepatic gastrointestinal stromal tumors (PHGIST). They have a poor prognosis and are historically difficult to diagnose. Our objective was to review and update the latest evidence-based knowledge concerning PHGIST, with a focus on epidemiology, etiology, pathophysiology, clinical presentation, histopathology, and treatment. These tumors are usually found incidentally, occur sporadically, and are associated with mutations of KIT and PDGFRA genes. PHGIST is a diagnosis of exclusion, as it has the same molecular, immunochemistry and histological appearance as gastrointestinal stromal tumors (GIST). Thus, imaging, such as positron emission tomography-computed tomography (PET-CT) must be used to rule out metastatic GIST before a diagnosis can be made. However, with mutation analysis and pharmacological advances, tyrosine kinase inhibitors are typically pursued with or without surgical intervention. Other potential treatments include transcatheter arterial chemoembolization and tumor ablation. However, these are typically considered palliative options. As there are only a limited number of publications regarding PHGIST, data concerning morbidity and mortality are not yet available. Immunohistopathology can help develop screening guidelines and evaluating resistance to treatment.

Novel Molecular Therapies and Genetic Landscape in Selected Rare Diseases with Hematologic Manifestations: A Review of the Literature

Rare diseases affect less than 1 in 2000 people and are characterized by a serious, chronic, and progressive course. Among the described diseases, a mutation in a single gene caused mastocytosis, thrombotic thrombocytopenic purpura, Gaucher disease, and paroxysmal nocturnal hemoglobinuria (KIT, ADAMTS13, GBA1, and PIG-A genes, respectively). In Castleman disease, improper ETS1, PTPN6, TGFBR2, DNMT3A, and PDGFRB genes cause the appearance of symptoms. In histiocytosis, several mutation variants are described: BRAF, MAP2K1, MAP3K1, ARAF, ERBB3, NRAS, KRAS, PICK1, PIK3R2, and PIK3CA. Genes like HPLH1, PRF1, UNC13D, STX11, STXBP2, SH2D1A, BIRC4, ITK, CD27, MAGT1, LYST, AP3B1, and RAB27A are possible reasons for hemophagocytic lymphohistiocytosis. Among novel molecular medicines, tyrosine kinase inhibitors, mTOR inhibitors, BRAF inhibitors, interleukin 1 or 6 receptor antagonists, monoclonal antibodies, and JAK inhibitors are examples of drugs expanding therapeutic possibilities. An explanation of the molecular basis of rare diseases might lead to a better understanding of the pathogenesis and prognosis of the disease and may allow for the development of new molecularly targeted therapies.

An integrative investigation of developmental toxicities induced by triphenyltin in a larval coral reef fish, Amphiprion ocellaris

Triphenyltin (TPT) is widely distributed on coastlines, which makes coral reef fish a potential target of TPT pollution. However, the negative effects of TPT on coral reef fish remain poorly understood. Therefore, in the present study, the larval coral reef fish Amphiprion ocellaris was used to investigate the developmental toxicities of TPT at environmentally relevant concentrations (0, 1, 10 and 100 ng/L). After TPT exposure for 14 d, the cumulative mortality increased, and growth was suppressed. In addition, TPT exposure inhibited the development of melanophores and xanthophores and delayed white strip formation, which might be responsible for the disruption of the genes (erbb3b, mitfa, kit, xdh, tyr, oca2, itk and trim33) related to pigmentation. TPT exposure also attenuated ossification of head skeletal elements and the vertebral column and inhibited the expression of genes (bmp2, bmp4 and sp7) related to skeletal development. The observed developmental toxicities on growth, pigmentation and skeleton development might be associated with the disruption of thyroid hormones and the genes related to thyroid hormone regulation (tshβ, thrα, thrβ, tg, tpo, dio2, and ttr). In addition, TPT exposure interfered with locomotor and shoaling behavior, and the related genes dbh, avp and avpr1aa. Taken together, our results suggest that TPT pollution might threaten the development of one of the most iconic coral reef fish, which might produce disastrous consequences on the health of coral reef ecosystems.

Molecular Dynamics Simulation of KIT Mutation in a Patient wıth Piebaldism, Congenital Cataract and Aphakic Glaucoma

Background: Piebaldism (OMIM #172800) is a rare autosomal dominant genodermatosis characterized by congenital poliosis and stable patches of leucoderma. Piebaldism is caused by mutations in the KIT and SNAI2 genes. The most common mutations are detected in the KIT gene. Case presentation: A 5-year-old boy, who was followed-up for aphakic glaucoma after congenital cataract surgery, was consulted to the medical genetics and dermatology departments due to premature graying of the hair, white forelock in the frontal region of the scalp, whitening in the inner part of the eyebrows and eyelashes and patchy leukoderma with hyperpigmented islands inside on the extremities and trunk. DNA sequencing revealed a heterozygous missense c.1861G&amp;gt;A mutation in the KIT gene. Mutation was evaluated using in silico 3D-structure analysis and bioinformatics tools Conclusion: KIT gene has a critical role in melanoblast migration, proliferation, differentiation and survival and molecular dynamics simulation and modeling proved that this variant inhibits the migration of melanoblasts and melanocytes by reducing the enzymatic activity of the KIT protein.

Antimicrobial efficacy of Thymus vulgaris extract against some Staphylococcus species isolated from subclinical mastitis in cattle in Basrah province, Iraq.

Thymus vulgaris extracts can play a significant role as alternatives for antimicrobial agents against bovine staphylococcus mastitis. This research's goal was to evaluate the antibacterial properties of an extract from T. vulgaris as an alternative to antibiotics for bovine Staphylococcus mastitis. In addition, it is important to know the effect of the extraction methods (hot alcoholic, cold alcoholic, and hot water extract) on their effectiveness. Two hundred ten cow milk samples from different areas of Basrah province had been suffering subclinical mastitis reported by using the California mastitis test (CMT). Staphylococcus species were identified by conventional microbiological technique, GP24 Kit, and nuc gene. Antimicrobial activity of various concentrations of T. vulgaris extracted (75, 50, 25) mg/ml with different methods of extraction (hot alcoholic, cold alcoholic, and hot water extract). Out of 210 samples, 99 (47.1%) were positive for the CMT, and the identification rate of Staphylococci spp. by conventional microbiological technique and GP24 kit was 78 (78.8%). Out of 78 isolates of Staphylococcus spp. 48 (61.5%) were identified as Staphylococcus aureus, by using both molecular techniques using PCR and miniaturized Kit GP24 and employing the miniature GP24, the remaining 30 (38.5%) were determined to be different species of Staphylococcus. Antibacterial activity of various concentrations of T. vulgaris extracted (75, 50, 25) mg/ml with different methods of extraction revealed that hot alcoholic extract (100%) was more effective than cold alcoholic extract (66.7%), whereas there is no effect on the bacteria species with the hot water extract. Thymus vulgaris extracts can play a significant role as alternatives for antimicrobial agents against bovine staphylococcus mastitis.

PATIENT MANAGEMENT TACTICS AT DIFFERENT STAGES OF GASTROINTESTINAL STROMAL TUMORS (GIST).

The aim: To analyze the results of treatment even in limited groups of patients. Materials and methods: Clinical cases of GIST based on the materials of the surgical clinic of the Central Municipal Hospital in Uzhgorod (Transcarpathian region) were discussed. Clinical, ultrasound and CT monitoring was provided. CT dynamics were assessed according to RECIST 1.1. Conclusions: Only surgery resection is enough in case of the "small" tumor originated from the stomach. Otherwise, in case of locally-widespread GIST it is expedient to refrain from radical surgical intervention. High-grade GIST was verified by the IHC examination with mutation of the KIT gene in exon 11. Imatinib mesylate 400 mg PO daily was prescribed. More than 1-year follow-up result: firstly more than 50% reduction of the tumor size with subsequent stabilization of the disease. Minimally invasive processes allow surgical interventions and do not require aggressive adjuvant therapy. The presence of a giant GIST is a serious diagnostic and treatment challenge. Only management of the patient by a multidisciplinary team allows to resolve diagnostic and treatment contradictions, to create the prospect of achieving complete or partial remission and long-term survival.

KERAGAMAN GENETIK BULU BABI TRIPNEUTES GRATILLA (LINNAEUS, 1758) DI PERAIRAN PANTAI DESA LAMBAKARA, SUMBA TIMUR, NUSA TENGGARA TIMUR (NTT)

A total of 14 samples were taken from the coastal waters of East Sumba. The sample was isolated from genomic DNA using the KIT GENE AID method using GO TAQ Green PCR Mix material and universal primer pairs LCO1490 and HCO2198 to determine the expression of the amplified COI gene (PCR). The PCR results were sent to First Base CO (Malaysia) for sequencing. The sequence length of the COI gene sequencing of the genus Tripneustes from NTT waters using universal primers LCO1490 and HCO2198 was 690-700 bp. The results showed that the genetic diversity of the sea urchin population in the coastal waters of Sumba was 0.83516 while the value of nucleotide diversity was 0.00516. The total genetic distance ranged from 0.000-0.010. All population genetic distances are still relatively low because genetic distances less than 0.010-0.099 are included in the low category. This close genetic distance causes connectivity between the two populations because there is gene flow. Based on the phylogenetic analysis, it was found that the populations in Sumba waters and some areas (outgroups) were genetically close

Implementation of multigene panel testing for breast and ovarian cancer in South Africa: A step towards excellence in oncology for the public sector.

Translation of genomic knowledge into public health benefits requires the implementation of evidence-based recommendations in clinical practice. In this study, we moved beyond BRCA1/2 susceptibility testing in breast and ovarian cancer patients to explore the application of pharmacogenetics across multiple genes participating in homologous recombination DNA damage repair. This involved the utilisation of next-generation sequencing (NGS) at the intersection of research and service delivery for development of a comprehensive genetic testing platform in South Africa. Lack of international consensus regarding risk categorization of established cancer susceptibility genes and the level of evidence required for prediction of drug response supported the development of a central database to facilitate clinical interpretation. Here we demonstrate the value of this approach using NGS to 1) determine the variant spectrum applicable to targeted therapy and implementation of prevention strategies using the 15-gene Oncomine™ BRCA Expanded Panel, and 2) searched for novel and known pathogenic variants in uninformative cases using whole exome sequencing (WES). Targeted NGS performed as a routine clinical service in 414 South African breast and/or ovarian cancer patients resulted in the detection of 48 actionable variants among 319 (15%) cases. BRCA1/2-associated cancers were identified in 70.8% of patients (34/48, including two double-heterozygotes), with the majority (35.3%, 12/34) representing known South African founder variants. Detection of actionable variants in established non-BRCA1/2 risk genes contributed 29% to the total percentage (14/48), distributed amongst ATM, CHEK2, BARD1, BRIP1, PALB2 and TP53. Experimental WES using a virtually constructed multi-cancer NGS panel in 16 genetically unresolved cases (and four controls) revealed novel protein truncating variants in the basal cell carcinoma gene PTCH1 (c.4187delG) and the signal transmission and transduction gene KIT (c.930delA) involved in crucial cellular processes. Based on these findings, the most cost-effective approach would be to perform BRCA1/2 founder variant testing at referral, followed by targeted multigene panel testing if clinically indicated and addition of WES in unresolved cases. This inventive step provides a constant flow of new knowledge into the diagnostic platform via a uniquely South African pathology-supported genetic approach implemented for the first time in this context to integrate research with service delivery.

W locus alleles of the KIT Gene in Turkish Van Cats and Their Association with Certain Phenotypes

Objective: Turkish Van cat is special cat breed in the world. The most important characteristics of the Turkish Van cats are the white and silky fur, and different eyes color. W locus of KIT gene was found to be an important gene for the white fur. However, there is not enough information about W locus of Turkish Van cats. The aim of this study was to determine the genotypic distribution of W locus alleles in Turkish Van cats and association between alelles and certain phenotypes.&#x0D; Material and Method: 48 Turkish Van cats bred in Van Yüzüncü Yıl University Van Cat Research and Application Center were selected for this study. DNA isolations were carried out from oral swaps and W locus genotyping of these cats was done by PCR. The Chi-square test was used to determine the association between the alleles and certain phenotypes.&#x0D; Results: It was shown that 41.67%, 22.92%, 18.75% and 16.67% of cats carried W/W, W/w+, w+/w+and W/ws, respectively. Frequencies of W locus alleles were found to be 61.45%, 30.21%, 8.33% for W, w+, ws, respectively. An association between detected genotypes and the phenotypic characters including eye color, head spotting, and hair length, could not be established.&#x0D; Conclusion: Turkish Van cats can carry white (W), white spotting (ws), and wild-type (w+) alleles in the W locus. No association between W locus alleles and eye color, head spotting, and fur length indicates other genetic variations should be addressed to understand genetical backround of the cats.

Mechanism of KIT gene regulation by GATA1 lacking the N-terminal domain in Down syndrome–related myeloid disorders

Children with Down syndrome (DS) are at high risk of transient abnormal myelopoiesis (TAM) and myeloid leukemia of DS (ML-DS). GATA1 mutations are detected in almost all TAM and ML-DS samples, with exclusive expression of short GATA1 protein (GATA1s) lacking the N-terminal domain (NTD). However, it remains to be clarified how GATA1s is involved with both disorders. Here, we established the K562 GATA1s (K562-G1s) clones expressing only GATA1s by CRISPR/Cas9 genome editing. The K562-G1s clones expressed KIT at significantly higher levels compared to the wild type of K562 (K562-WT). Chromatin immunoprecipitation studies identified the GATA1-bound regulatory sites upstream of KIT in K562-WT, K562-G1s clones and two ML-DS cell lines; KPAM1 and CMK11-5. Sonication-based chromosome conformation capture (3C) assay demonstrated that in K562-WT, the − 87 kb enhancer region of KIT was proximal to the − 115 kb, − 109 kb and + 1 kb region, while in a K562-G1s clone, CMK11-5 and primary TAM cells, the − 87 kb region was more proximal to the KIT transcriptional start site. These results suggest that the NTD of GATA1 is essential for proper genomic conformation and regulation of KIT gene expression, and that perturbation of this function might be involved in the pathogenesis of TAM and ML-DS.

Molecular-Targeted Therapy for Tumor-Agnostic Mutations in Acute Myeloid Leukemia.

Comprehensive genomic profiling examinations (CGPs) have recently been developed, and a variety of tumor-agnostic mutations have been detected, leading to the development of new molecular-targetable therapies across solid tumors. In addition, the elucidation of hereditary tumors, such as breast and ovarian cancer, has pioneered a new age marked by the development of new treatments and lifetime management strategies required for patients with potential or presented hereditary cancers. In acute myeloid leukemia (AML), however, few tumor-agnostic or hereditary mutations have been the focus of investigation, with associated molecular-targeted therapies remaining poorly developed. We focused on representative tumor-agnostic mutations such as the TP53, KIT, KRAS, BRCA1, ATM, JAK2, NTRK3, FGFR3 and EGFR genes, referring to a CGP study conducted in Japan, and we considered the possibility of developing molecular-targeted therapies for AML with tumor-agnostic mutations. We summarized the frequency, the prognosis, the structure and the function of these mutations as well as the current treatment strategies in solid tumors, revealed the genetical relationships between solid tumors and AML and developed tumor-agnostic molecular-targeted therapies and lifetime management strategies in AML.

New C3H KitN824K/WT cancer mouse model develops late-onset malignant mammary tumors with high penetrance

Gastro-intestinal stromal tumors and acute myeloid leukemia induced by activating stem cell factor receptor tyrosine kinase (KIT) mutations are highly malignant. Less clear is the role of KIT mutations in the context of breast cancer. Treatment success of KIT-induced cancers is still unsatisfactory because of primary or secondary resistance to therapy. Mouse models offer essential platforms for studies on molecular disease mechanisms in basic cancer research. In the course of the Munich N-ethyl-N-nitrosourea (ENU) mutagenesis program a mouse line with inherited polycythemia was established. It carries a base-pair exchange in the Kit gene leading to an amino acid exchange at position 824 in the activation loop of KIT. This KIT variant corresponds to the N822K mutation found in human cancers, which is associated with imatinib-resistance. C3H KitN824K/WT mice develop hyperplasia of interstitial cells of Cajal and retention of ingesta in the cecum. In contrast to previous Kit-mutant models, we observe a benign course of gastrointestinal pathology associated with prolonged survival. Female mutants develop mammary carcinomas at late onset and subsequent lung metastasis. The disease model complements existing oncology research platforms. It allows for addressing the role of KIT mutations in breast cancer and identifying genetic and environmental modifiers of disease progression.

Prospective Evaluation of Sorafenib Combined with Chemotherapy in Newly Diagnosed Adult Core-Binding Factor Acute Myeloid Leukemia: An Open-Label, Randomized Controlled, Multicenter Phase II Trial

Objective Core-binding factor acute myeloid leukemia (CBF-AML) includes AML with t(8;21)(q22;q22) and inv(16)(p13q22)/t(16;16)(p13;q22) chromosomal rearrangements, leading to the RUNX1-RUNX1T1 and CBFB-MYH11 fusion genes, respectively. Although CBF-AML is considered to have a favorable prognosis relative to other AML subtypes, up to 40% of these patients experience relapse. Recent studies demonstrate achievement of complete molecular remission (CMR) at the end of treatment significantly associated with a reduced risk of relapse. A high frequency of mutations and/or high expression of KIT gene is observed in CBF-AML. Sorafenib is a first-generation type-II multitargeted tyrosine kinase receptor inhibitor (TKI) that suppresses various signaling pathways associated with the development of AML, such as RTK (FLT3, c-KIT). Thus the purpose of this study is to evaluate the safety and efficacy of sorafenib combined with chemotherapy in adult newly diagnosed CBF-AML. Methods Patients were randomly assigned (1:1) to control group (chemotherapy alone) or sorafenib group (sorafenib combined with chemotherapy). For control group, patients received one cycle of induction therapy with idarubicin (12 mg/m² on days 1-3) plus cytarabine (100 mg/m² on days 1-7), followed by one cycle of idarubicin (8 mg/m² on days 1-3) plus cytarabine (2 g/m² q12h on days 1-3) and two cycles of high-dose cytarabine consolidation therapy (2 g/m² q12h on days 1-3). For sorafenib group, patients were treated with chemotherapy plus sorafenib at 400 mg twice daily on days 8-21 for induction cycle, and on days 1-21 for each consolidation, and as maintenance for 12 months. Allogeneic or autologous HSCT were implemented based on the measurable residual disease (MRD) level and donor availability after 4 cycles of therapy. MRD levels were serially monitored for RUNX1-RUNX1T1 or CBFB-MYH11 transcripts by real-time quantitative polymerase chain reaction. Results were expressed as a [fusion gene/ABL1] ×100 transcript ratio. Major molecular response (MMR) and complete molecular remission (CMR) are defined as transcript ratio < 0.1% and 0.001%, respectively. The primary endpoint was CMR after 4 cycles of therapy in bone marrow (BM). Results Between January 2020 and March 2022, 64 patients were enrolled and randomly assigned to sorafenib group (n=32) or control group (n=32). There is no significant difference between the two groups about age, gender, CBF subtype, BM blast percentage, additional chromosome abnormalities and gene mutations at diagnosis. The hematological complete remission in the sorafenib and control group were 96.9% and 94.1%, respectively (p=.592). Following three cycles of therapy, MMR was observed in 79.3% of the sorafenib group and 46.9% of the control group (p =.009). Sorafenib group also had a significantly higher CMR than control group (62.1% vs 28.1%, p =.009). After four cycles of therapy, MMR increased to 100% in the sorafenib group and 70.8% in the control group (p =.019), whileCMR was also more frequently achieved in the sorafenib group than that in the control group (90.9% vs 54.2%, p =.006). There was no significant difference of grades 3-4 adverse events between the two groups. Grade 4 neutropenia (neutrophil count less than 0.5×10⁹ cells per L) and thrombocytopenia (platelet count less than 20×10⁹ per L) were observed in all cases. The median duration of neutropenia was 12d (range, 6-25d) in the sorafenib group and 10d (range, 5-22d) in the control group (p =.063) , while the median duration of thrombocytopenia was 12d (range, 5-33d) and 9d (range, 6-19d) (p =.052), respectively.The most common grade 3-4 non-hematological adverse events in sorafenib and control group were pneumonia (31.3% vs 57.4%, p=.019), mucositis (21.9% vs 24.1%, p =.816), blood stream infection (37.5% vs 31.5%, p =.568). Conclusion Sorafenib combined with chemotherapy significantly increased the CMR after 4 cycles of therapy, however, the incidence of haematological and non-haematological adverse events did not apparently increased. The impact of sorafenib combined with chemotherapy on relapse and survival of CBF-AML need further following-up. Keywords: Sorafenib, CBF-AML, CMR, adverse events

Preliminary Safety and Efficacy from Apex, a Phase 2 Study of Bezuclastinib (CGT9486), a Novel, Highly Selective, Potent KIT D816V Tyrosine Kinase Inhibitor, in Adults with Advanced Systemic Mastocytosis (AdvSM)

Background: Systemic mastocytosis (SM) is a rare disease characterized by the proliferation of mast cells (MC). In about 95% of adult patients, SM is driven by a gain-of-function mutation (D816V) in exon 17 of the KIT gene. Advanced SM (AdvSM) is an aggressive, life-threatening form of SM and includes three subtypes; aggressive SM (ASM), SM with an associated hematologic neoplasm (SM-AHN), and MC leukemia (MCL). Bezuclastinib is an oral, highly selective, and potent tyrosine kinase inhibitor (TKI) with specificity for mutations in KIT exons 9, 11, 17, and 18, including D816V, while sparing closely related kinases (e.g., PDGFRα, PDGFRβ, and CSF1R). Results from a phase 1/2 study in patients with advanced solid tumors coupled with preclinical data have led to the on-going evaluation of bezuclastinib in patients with AdvSM, the Apex study (NCT04996875). The primary objective of this study is to evaluate the safety, efficacy, pharmacokinetic (PK), and pharmacodynamic (PD) profile of bezuclastinib in all AdvSM subtypes. Methods: Apex is a Phase 2, open-label, 2-part, multicenter study in adult patients with AdvSM per WHO diagnostic criteria, who have measurable SM-related organ damage according to modified IWG-MRT-ECNM consensus eligibility and response criteria (mIWG), and have a baseline serum tryptase of ≥20 ng/mL. Patients with a history of prior TKI therapy (e.g., avapritinib, midostaurin) are permitted in the study. In Part 1, patients are randomized 1:1:1:1 to bezuclastinib 50, 100, or 200 mg BID, or 400 mg QD. Data from Part 1 will inform dose selection for Part 2. The primary efficacy endpoint for this study is overall response rate (complete response [CR], CR with incomplete hematologic recovery [CRh], partial response [PR] and clinical improvement [CI]) as assessed by a Central Response Review Committee and based on mIWG response criteria. Results: As of May 24, 2022, 11 mIWG evaluable patients with AdvSM (ASM: n=2, SM-AHN: n=8, and MCL: n=1) were randomized in Part 1 to 50mg BID (n=3), 100mg BID (n=3), 200mg BID (n=3), and 400mg QD (n=2). The majority of patients were male (82%) and treatment naïve (82%) with ECOG PS 0-1 (82%) and positive for KIT D816V (91%). Median (range) BM MC burden and serum tryptase at baseline were 30% (7-80%) and 182 ng/mL (68-1578 ng/mL), respectively. Bezuclastinib was well-tolerated across all dose levels. Treatment Emergent Adverse Events (TEAEs) reported in >1 patient included anemia (n=3), neutropenia (n=2), and thrombocytopenia (n=2), a majority of which were low-grade. One serious AE of hypersensitivity (mediator flare) was reported. Two patients had an AE-related dose reduction with one patient subsequently re-escalating to the randomized dose. Preliminary clinical activity data showed that all 11 patients experienced a >50% reduction in serum tryptase from baseline, 10/11 (91%) within the first week of treatment; 6 (55%) patients achieved a serum tryptase level <20 ng/mL, 4/6 within the first cycle of treatment. Among patients with available data after ≥2 cycles of treatment, all 8 achieved a median reduction of 68% in KIT D816V variant allele fraction (VAF) and ≥50% reduction in BM MC, with 6/8 (75%) achieving complete clearance of MC aggregates. There were no reported instances of cognitive effects or intracranial bleeding. Conclusion: Early data suggest that bezuclastinib is well-tolerated and is associated with encouraging early signs of clinical activity as demonstrated by meaningful reductions in serum tryptase, MC burden, and KIT D816V VAF. Enrollment is currently ongoing. Updated safety and clinical activity as well as initial clinical objective response data will be presented.

NGS Testing Practices and Molecular Profile Landscape of the KIT Gene in Systemic Mastocytosis: Real-World Insights from Selected European Countries

NGS Testing Practices and Molecular Profile Landscape of the KIT Gene in Systemic Mastocytosis: Real-World Insights from Selected European Countries

Novel pathogenic variants in KIT gene in three Chinese piebaldism patients.

Piebaldism is a rare autosomal dominant disease, and roughly 75% patients had KIT gene mutations. Up to date, approximately 90 KIT mutations causing piebaldism were reported. To identify KIT gene mutations in three pediatric piebaldism patients from different families and explore the genotype-phenotype correlation, peripheral blood DNA were collected from probands and their parents. Whole-exome sequencing was performed to detect potential disease-causing variants in the three probands. Putative variants were validated by Sanger sequencing. Heterozygous variants of c.2469_2484del (p.Tyr823*), c.1994G > C (p.Pro665Leu), and c.1982_1983insCAT (p.662_663insIle) in KIT gene were detected in three probands. These variants were all novel and classified as pathogenic/likely pathogenic variants according to the interpretation guidelines of American College of Medical Genetics and Genomics and the Association for Molecular Pathology. The probands carrying variants located in tyrosine kinase domain exhibited a more severe phenotype. The piebaldism in three families was caused by novel heterozygous KIT variants. The severity of phenotypes is related with the types and locations of different mutations. Our results further provided evidence for genetic counseling for the three families.