PDGFRA exon 18 mutation

P1, N=240, Recruiting, IDRx, Inc. | N=143 --> 240

One model is characterized by an imatinib-resistant PDGFRA exon 18 p.D842V mutation... We are expanding our established platform of well-characterized GIST PDX models, that were proven to serve as an excellent tool for preclinical drug testing and tumor biology studies. The platform is available for cooperative projects with academic and commercial partners.

Transarterial radioembolisation, followed by systemic gemcitabine/cisplatin therapy induced long-term remission...Therefore, due to the progressive hepatocellular component, the patient received atezolizumab/bevacizumab with induced tumor devascularization and AFP normalization. However, after six months, the therapy was changed to FOLFIRI due to progressive disease with lung, liver and lymph node involvement and an increase in CA19-9... In 2020, a 50-year-old male patient presented to our department with weight loss and pain in the right upper abdomen. CT and MRI imaging of the liver showed a 20-cm diffusely growing tumour involving all liver segments and multiple satellite lesions. Histologic examination confirmed the diagnosis of a poorly differentiated cHCC-CCA.

If a patient progresses on imatinib, there are additional FDA-approved treatments (sunitinib, regorafenib, ripretinib), which are not currently available for those patients that progress on avapritinib. Our model has the potential to identify which PDGFRA exon 18 mutant GIST patients would benefit from front-line imatinib therapy, while subsequently identifying those that would require avapritinib treatment. Avapritinib was recently approved for first-line treatment for all PDGFRA exon 18 mutant GIST in the United States. Imatinib has been used clinically for over two decades, and is more cost-effective and has a superior safety and tolerability profile compared to avapritinib.

uPARAP is highly expressed in several GIST xenograft models across multiple passages of ex-mouse tumors. Considering its preferential expression in GIST and other mesenchymal tumors and the recycling character of this molecular target, uPARAP may serve as a powerful emerging target for systemic treatment of GIST beyond traditional kinase inhibitors or in combination with the latter. uPARAP positive xenograft models can be used for in vivo evaluation of such anti-uPARAP treatment.

However, following initiation of first-line imatinib, a tyrosine kinase inhibitor (TKI), nearly all patients will develop resistance within 2 years through the emergence of secondary resistance mutations in KIT, typically in the Adenosine Triphosphate (ATP)-binding site or activation loop of the kinase domain...To target resistance, research efforts are primarily focused on developing next-generation inhibitors of KIT and/or PDGFRA, which can inhibit alternate receptor conformations or unique mutations, and compounds that impact complimentary pathogenic processes or epigenetic events. Here, we review the literature on the medical management of high-risk localized and advanced GIST and provide an update on clinical trial approaches to this disease.

DL models yielded comparable results to the Miettinen classification for relapse-free-survival prediction in localized GIST without adjuvant Imatinib (C-index=0.83 in cross-validation and 0.72 for independent testing)...Additionally, novel histological criteria predictive of patients' outcome and mutations were identified by reviewing the tiles selected by the models. As a proof of concept, our study showed the possibility of implementing DL with digitized WSI and may represent a reproducible way to improve tailoring therapy and precision medicine for patients with GIST.

Indeed, with the latter setting 4 patients out of 5 were correctly predicted as non-responders. The results are a first step towards using radiomics to improve the management of patients with GIST, especially when tumor tissue is unavailable for molecular analysis or when molecular profiling is inconclusive.

This identified an oncogenic mutation in exon 18 of the PDGFRA gene, which is characteristic for inflammatory fibroid polyps of the gastrointestinal tract. To the best of our knowledge, this is the first case of an IFP in the urogenital tract.

P3; CtDNA sequencing efficiently detects KIT/PDGFRA mutations and prognosticates outcomes in patients with TKI-resistant GIST treated with avapritinib. ctDNA analysis can be used to monitor disease progression and provide more personalized treatment.

The miRNA-mRNA networks highlighted a signature of miRNAs/mRNA that could explain the indolent behavior of the D842V mutated GIST. The results highlighted a different miRNA fingerprint in PDGFRA D842V GISTs compared to non-D842Vmutated patients, which could explain the different biological behavior of this GIST subset.

Avapritinib levels in patients' CSF and brain tumor tissue reached micromolar levels. These results demonstrate that avapritinib is a potent, selective, and CNS-penetrant PDGFRA/KIT inhibitor that is promising for further study in pHGG with relevant alterations.

Based on our data, over half of the unique and complex mutations observed in our PDGFRA-mutant GIST patient cohort would be predicted to be imatinib sensitive. Our predictive model has the potential to identify which patients with PDGFRA exon 18 mutant-GIST would benefit from front-line imatinib therapy as an alternative to avapritinib. Conversely, we could also identify those patients who would require treatment with front-line avapritinib.

Objective: The majority of gastrointestinal stromal tumors (GISTs) are driven by constitutively activated kinases, either KIT or PDGFRA, and respond to treatment with tyrosine kinase inhibitors (TKI) such as imatinib, sunitinib, regorafenib, and ripretinib. Not applicable

The discovery of imatinib with promising anti-tumor effect and successive tyrosine kinase inhibitors (TKI), including second-line sunitinib and third-line regorafenib, revolutionized the management of advanced and metastatic GIST over the past two decades. Recently, ripretinib and avapritinib were approved for the fourth line setting and for PDGFRA exon 18-mutant GIST in first-line setting, respectively...KIT/PDGFRα wild-type GISTs are generally less sensitive to imatinib and late-line TKIs. Recent studies demonstrated that targeting fibroblast growth factor receptor signaling may be a potential target for the wild-type GISTs.

P1, N=143, Recruiting, IDRx, Inc. | Not yet recruiting --> Recruiting

P1, N=143, Not yet recruiting, IDRx, Inc.

These data confirm that c-KIT exon 11 mutations occur frequently in canine GISTs, and identify the presence of a PDGFRA mutation similar to human GISTs. This study also suggests a potential association of c-KIT mutation with more aggressive biological behavior.

ctDNA mutations were not detectable when patients responded to a switch in TKI therapy. In conclusion, detection of GIST-related mutations in ctDNA using a customized targeted NGS panel represents an attractive non-invasive means to obtain clinically tractable information at the time of disease progression.

Part 2 will enroll ≥ 25 patients at the recommended avapritinib dose from Part 1; primary endpoint is objective response rate. Avapritinib once-daily will be administered in continuous 28-day cycles.

Systemic mastocytosis is a rare hematologic disorder characterized by the clonal proliferation of mast cells in extra-cutaneous organs. This disease can be further subdivided into five different phenotypes: indolent systemic mastocytosis (ISM), smoldering systemic mastocytosis (SSM), aggressive systemic mastocytosis (ASM), systemic mastocytosis with an associated hematological neoplasm (SM-AHN) and mast cell leukemia (MCL). The tyrosine kinase inhibitor (and also potent KIT D816V inhibitor) avapritinib, initially approved for the treatment of gastrointestinal stromal tumors (GISTs) bearing a PDGFRA exon 18 mutation, also showed great promise in patients with systemic mastocytosis, a disease known to be driven by a mutation in KIT (D816V). We present an overview of this rare disorder, including a review of the current understanding of the genetic mechanisms which lead to the disease state, the action of the tyrosine kinase inhibitors, as well as the latest clinical trial data which led to the current recommendations for the use of avapritinib.

Inclusion criteria: (1) patients aged older than 18 years; (2) patients who were diagnosed with GIST based on pathology; (3) patients without surgery, whose preoperative imaging evaluation of GIST found the violations of the surrounding organs or partial transfer of an estimated difficulty to achieve R0 resection, or the maximum diameter of the tumor > 10 cm, or the liver metastasis, or the expectation of higher risk of surgical complications; (4) patients who were treated with the imatinib 400 mg/d for the first time; (5) Eastern Cooperative Oncology Group (ECOG) score of 0-2...When the DOG-1 content decreased by more than 57.5% 1-month after treatment, it can be used as an indicator to judge the effectiveness of the treatment, whose sensitivity was 72.2% and specificity was 100%. The detection of peripheral blood CTC can evaluate the efficacy of targeted therapy in GIST patients and can provide decision-making basis for further clinical treatment.

Among the 61 cases of primary localized GIST undergoing complete surgical resection, 2 cases were intermediate-risk GIST, 5 cases were low-risk GIST, and 1 case was very low-risk GIST, of whom 1 case of intermediate-risk GIST received 1-year adjuvant imatinib mesylate (IM) therapy after operation, and no tumor recurrence developed during the follow-up period...Of 9 patients directly receiving neoadjuvant targeted therapy (IM or avapritinib), 5 had complete imaging follow-up data, and the evaluation of efficacy achieved PR...Compared with GIST patients with "heterozygous mutation" in KIT exon 11, GIST patients with "homozygous mutation" in KIT exon 11 are more likely to relapse after surgery and to develop resistance to IM. Therefore, it is still necessary to seek more effective treatment methods for this subset of cases.

Based on its unprecedented activity, avapritinib should be considered as first-line therapy for GIST patients harboring this mutation. We strongly recommend to determine KIT/PDGFRA genotype in order to identify the different GIST molecular subtypes and guide treatment decision.

Approval of imatinib, a KIT/PDGFRA tyrosine kinase inhibitor (TKI), meaningfully improved the treatment of advanced GIST. Other TKIs subsequently gained approval: sunitinib as a second-line therapy and regorafenib as a third-line therapy...Avapritinib, a type I kinase inhibitor that targets active conformation, was approved for the treatment of adults with unresectable or metastatic GIST harboring a PDGFRA exon 18 mutation, including PDGFRA D842V mutations. In this review, we will discuss how resistance mutations have driven the need for newer treatment options for GIST and compare the original GIST TKIs with the next-generation KIT/PDGFRA kinase inhibitors, ripretinib and avapritinib, with a focus on their mechanisms of action.

The treatment with avapritinib was stopped and the patient received corticosteroid and corneal regenerating agents. The symptoms resolved within 1 month and the patient has remained on stable disease at two subsequent adjusted avapritinib doses (100 mg once daily) for over 1 year.

In the last 20 years, a treatment algorithm for patients with advanced GISTs, which includes imatinib, sunitinib, and regorafenib as first-, second-, and third-line therapies, respectively, has been established. Recently, 2 new TKIs have been approved: ripretinib for fourth-line therapy and avapritinib as first-line therapy in patients harboring platelet-derived growth factor receptor α (PDGFRA) exon 18 D842V mutations...All of these therapies have varying efficacies and safety profiles that warrant an updated treatment landscape review. This review article summarizes the efficacy and safety data currently available for conventional TKIs along with recently approved and experimental therapies.

Several targeted therapies have also improved survival in GIST patients after progression on imatinib including sunitinib and regorafenib. Recently, United States Federal and Drug Administration (FDA) approved two new tyrosine kinase inhibitors for the treatment of heavily pretreated advanced/unresectable GIST including avapritinib (a selective inhibitor for PDGFRA exon 18 mutation including D842V mutations) and ripretinib (a broad-spectrum kinase inhibitor of c-Kit and PDGFRA). In this article, we will provide a comprehensive review of GIST including the current standard of care treatment and exploring future paradigm shifts in therapy.

Sunitinib and regorafenib are multi-kinase inhibitors that can be used as second-line or third-line therapy in imatinib-resistant or -intolerant GISTs, respectively. Ripretinib (a switch-control tyrosine kinase inhibitor) has recently been approved for fourth-line treatment in metastatic GIST. The TKI avapritinib has been approved for metastatic GIST harboring the imatinib-resistant PDGFRA exon 18 mutation...After surgical resection, patients should resume tyrosine kinase inhibitor (TKI) therapy as soon as possible and be monitored for disease progression. In all patients with metastatic GIST, the decision to pursue metastasectomy for GIST should be made in a multidisciplinary setting and be individualized according to patient age, comorbidities, functional status, symptoms, mutation status, extent of disease, completeness of resection, TKI response, and goals of the patient.

In addition, the presence of succinate dehydrogenase-deficient GIST was found in 5 cases (3.6%). In conclusion, the tumor genotype with regard to KIT and PDGFRA mutations exhibited prognostic significance for the risk of GIST progression and may be helpful for the optimization of tailored adjuvant therapy.

These results suggest that adoption of avapritinib as a treatment option would have a minimal budget impact to a hypothetical US health plan. This would be primarily attributable to the small eligible patient population and cost offsets from reduced or delayed postprogression costs.

Second and third line options include sunitinib and regorafenib, respectively, and yield low response rates and limited clinical benefit. There have been recent FDA approvals for GIST including ripretinib in the fourth-line setting and avapritinib for PDGFRA exon 18-mutant GIST. This article aims to review the optimal treatment approach for the management of patients with advanced GIST. It examines the standard treatment options available but also explores the novel treatment approaches in the setting of imatinib refractory GIST.

Early recognition of adverse events and tailored dose modification appear to be effective approaches for managing treatment-related adverse events and maintaining patients on avapritinib. Dose reduction does not appear to result in reduced efficacy. Patients' cognitive function should be assessed at baseline and monitored carefully throughout treatment with avapritinib for the onset of cognitive adverse events. Dose interruption is recommended at the first sign of any cognitive effect, including grade 1 events.

Most GIST with PDGFRA exon 18 mutations including D842V mutation are highly resistant to imatinib...Among all the cases, 66 cases underwent R0 resection without preoperative treatment; two cases underwent emergency operation with R1 resection because of tumor rupture; 2 cases were not operated after the pathological and mutation types were confirmed by biopsy (one case received avapritinib treatment and obtain partial remission)...However, the above factros were not testified as independant prognostic facors in multivariate Cox analysis (all P<0.05). Clinicopathologic features and the efficacy of radical resection in patients with PDGFRA-D842V mutation are similar to those in patients with non-D842V mutation.

Avapritinib was developed to selectively target these mutations, thereby offering a new treatment option for patients in whom imatinib, sunitinib, and regorafenib have failed. This review covers the basic science and preclinical studies that guided avapritinib's development, in addition to the data currently available from early clinical studies as well as those later-stage trials that led to its approval.

We described a case of EGIST with a PDGFRA mutation arising in the lesser omentum. And we reviewed 57 cases of omental EGIST and showed that the clinicopathological characteristics and mutation status in omental EGIST were very similar to gastric GIST. In particular, PDGFAR D842V mutation rate in omental EGIST seemed as high as that in gastric GIST. These results suggested that omental EGIST is strongly related to gastric GIST, so the behavior of omental EGIST might be akin to gastric GIST. However, further studies are required to determine the prognosis and the necessity of adjuvant therapy for EGIST with a PDGFRA mutation.

Funding: Blueprint Medicines Corporation. Clinical trial identification: NCT02508532.