Ripretinib (DCC-2618) Is a Switch Control Kinase Inhibitor of a Broad Spectrum of Oncogenic and Drug-Resistant KIT and PDGFRA Variants

Kinase Inhibitors and Kinase-Targeted Cancer Therapies: Recent Advances and Future Perspectives

Over 120 small-molecule kinase inhibitors (SMKIs) have been approved worldwide for treating various diseases, with nearly 70 FDA approvals specifically for cancer treatment, focusing on targets like the epidermal growth factor receptor (EGFR) family. Kinase-targeted strategies encompass monoclonal antibodies and their derivatives, such as nanobodies and peptides, along with innovative approaches like the use of kinase degraders and protein kinase interaction inhibitors, which have recently demonstrated clinical progress and potential in overcoming resistance. Nevertheless, kinase-targeted strategies encounter significant hurdles, including drug resistance, which greatly impacts the clinical benefits for cancer patients, as well as concerning toxicity when combined with immunotherapy, which restricts the full utilization of current treatment modalities. Despite these challenges, the development of kinase inhibitors remains highly promising. The extensively studied tyrosine kinase family has 70% of its targets in various stages of development, while 30% of the kinase family remains inadequately explored. Computational technologies play a vital role in accelerating the development of novel kinase inhibitors and repurposing existing drugs. Recent FDA-approved SMKIs underscore the importance of blood-brain barrier permeability for long-term patient benefits. This review provides a comprehensive summary of recent FDA-approved SMKIs based on their mechanisms of action and targets. We summarize the latest developments in potential new targets and explore emerging kinase inhibition strategies from a clinical perspective. Lastly, we outline current obstacles and future prospects in kinase inhibition.

KIT ATP-Binding Pocket/Activation Loop Mutations in GI Stromal Tumor: Emerging Mechanisms of Kinase Inhibitor Escape

PURPOSE

Imatinib resistance in GI stromal tumors (GISTs) is primarily caused by secondary KIT mutations, and clonal heterogeneity of these secondary mutations represents a major treatment obstacle. KIT inhibitors used after imatinib have clinical activity, albeit with limited benefit. Ripretinib is a potent inhibitor of secondary KIT mutations in the activation loop (AL). However, clinical benefit in fourth line remains limited and the molecular mechanisms of ripretinib resistance are largely unknown.

PATIENTS AND METHODS

Progressing lesions of 25 patients with GISTs refractory to ripretinib were sequenced for KIT resistance mutations. Resistant genotypes were validated and characterized using novel cell line models and in silico modeling.

RESULTS

GISTs progressing on ripretinib were enriched for secondary mutations in the ATP-binding pocket (AP), which frequently occur in cis with preexisting AL mutations, resulting in highly resistant AP/AL genotypes. AP/AL mutations were rarely observed in a cohort of progressing GIST samples from the preripretinib era but represented 50% of secondary KIT mutations in patients with tumors resistant to ripretinib. In GIST cell lines harboring secondary KIT AL mutations, the sole genomic escape mechanisms during ripretinib drug selection were AP/AL mutations. Ripretinib and sunitinib synergize against mixed clones with secondary AP or AL mutants but do not suppress clones with AP/AL genotypes.

CONCLUSION

Our findings underscore that KIT remains the central oncogenic driver even in late lines of GIST therapy. KIT-inhibitor combinations may suppress resistance because of secondary KIT mutations. However, the emergence of KIT AP/AL mutations after ripretinib treatment calls for new strategies in the development of next-generation KIT inhibitors.

The GIST of it all: management of gastrointestinal stromal tumors (GIST) from the first steps to tailored therapy. A bibliometric analysis

PURPOSE

Improvement of patient care is associated with increasing publication numbers in biomedical research. However, such increasing numbers of publications make it challenging for physicians and scientists to screen and process the literature of their respective fields. In this study, we present a comprehensive bibliometric analysis of the evolution of gastrointestinal stromal tumor (GIST) research, analyzing the current state of the field and identifying key open questions going beyond the recent advantages for future studies to assess.

METHODS

Using the Web of Science Core Collection, 5040 GIST-associated publications in the years 1984-2022 were identified and analyzed regarding key bibliometric variables using the Bibliometrix R package and VOSviewer software.

RESULTS

GIST-associated publication numbers substantially increased over time, accentuated from year 2000 onwards, and being characterized by multinational collaborations. The main topic clusters comprise surgical management, tyrosine kinase inhibitor (TKI) development/treatment, diagnostic workup, and molecular pathophysiology. Within all main topic clusters, a significant progress is reflected by the literature over the years. This progress ranges from conventional open surgical techniques over minimally invasive, including robotic and endoscopic, resection techniques to increasing identification of specific functional genetic aberrations sensitizing for newly developed TKIs being extensively investigated in clinical studies and implemented in GIST treatment guidelines. However, especially in locally advanced, recurrent, and metastatic disease stages, surgery-related questions and certain specific questions concerning (further-line) TKI treatment resistance were infrequently addressed.

CONCLUSION

Increasing GIST-related publication numbers reflect a continuous progress in the major topic clusters of the GIST research field. Especially in advanced disease stages, questions related to the interplay between surgical approaches and TKI treatment sensitivity should be addressed in future studies.

KIT/PDGFRA inhibitors for the treatment of gastrointestinal stromal tumors: getting to the gist of the problem

INTRODUCTION

Approximately 90% of gastrointestinal stromal tumors (GISTs) are driven by activating mutations in receptor tyrosine-kinases KIT or PDGFRA. Despite the outstanding results of first-line imatinib in advanced GIST, resistance ultimately occurs mainly through secondary mutations in KIT/PDGFRA. Other tyrosine-kinase inhibitors (TKIs) with a broader spectrum of activity against these mutations are approved after imatinib failure. However, response rates and progression-free survival are drastically lower compared to imatinib. Notably, imatinib also triggers early tolerance adaptation mechanisms, which precede the occurrence of secondary mutations.

AREAS COVERED

In this review, we outline the current landscape of KIT inhibitors, discuss the novel agents, and present additional biological pathways that may be therapeutically exploitable.

EXPERT OPINION

The development of broad-spectrum and highly selective TKIs able to induce a sustained KIT/PDGFRA inhibition is the pillar of preclinical and clinical investigation in GIST. However, it is now recognized that the situation is more intricate, with various factors interacting with KIT and PDGFRA, playing a crucial role in the response and resistance to treatments. Future strategies in the management of advanced GIST should integrate driver inhibition with the blockade of other molecules to enhance cell death and establish enduring responses in patients.

Outcomes of Late-Line Systemic Treatment in GIST: Does Sequence Matter?

Ripretinib and avapritinib have demonstrated activity in the late-line treatment of gastrointestinal stomal tumors (GISTs). We investigated whether patients previously treated with ripretinib benefit from avapritinib, and vice versa. Patients diagnosed with metastatic/unresectable GIST and treated with both drugs at two institutions in 2000-2021 were included. Patients were grouped by drug sequence: ripretinib-avapritinib (RA) or avapritinib-ripretinib (AR). Radiographic response was evaluated using RECIST 1.1. Kaplan-Meier and log-rank tests were used to compare time-to-progression (TTP) and overall survival (OS). Thirty-four patients (17 per group) were identified, with a median age of 48 years. The most common primary site was the small bowel (17/34, 50%), followed by the stomach (10/34, 29.4%). Baseline characteristics and tumor mutations were not significantly different between groups. Response rates (RRs) for ripretinib were 18% for RA and 12% for AR; RRs for avapritinib were 12% for AR and 18% for RA. Median TTPs for ripretinib were 3.65 months (95%CI 2-5.95) for RA and 4.73 months (1.87-15.84) for AR. Median TTPs for avapritinib were 5.39 months (2.86-18.99) for AR and 4.11 months (1.91-11.4) for RA. Median OS rates following RA or AR initiation were 29.63 (95%CI 13.8-50.53) and 33.7 (20.03-50.57) months, respectively. Both ripretinib and avapritinib were efficacious in the late-line treatment of GIST, with no evidence that efficacy depended on sequencing.

Ripretinib versus sunitinib in gastrointestinal stromal tumor: ctDNA biomarker analysis of the phase 3 INTRIGUE trial

INTRIGUE was an open-label, phase 3 study in adult patients with advanced gastrointestinal stromal tumor who had disease progression on or intolerance to imatinib and who were randomized to once-daily ripretinib 150 mg or sunitinib 50 mg. In the primary analysis, progression-free survival (PFS) with ripretinib was not superior to sunitinib. In clinical and nonclinical studies, ripretinib and sunitinib have demonstrated differential activity based on the exon location of KIT mutations. Therefore, we hypothesized that mutational analysis using circulating tumor DNA (ctDNA) might provide further insight. In this exploratory analysis (N = 362), baseline peripheral whole blood was analyzed by a 74-gene ctDNA next-generation sequencing-based assay. ctDNA was detected in 280/362 (77%) samples with KIT mutations in 213/362 patients (59%). Imatinib-resistant mutations were found in the KIT ATP-binding pocket (exons 13/14) and activation loop (exons 17/18). Mutational subgroup assessment showed 2 mutually exclusive populations with differential treatment effects. Patients with only KIT exon 11 + 13/14 mutations (ripretinib, n = 21; sunitinib, n = 20) had better PFS with sunitinib versus ripretinib (median, 15.0 versus 4.0 months). Patients with only KIT exon 11 + 17/18 mutations (ripretinib, n = 27; sunitinib, n = 25) had better PFS with ripretinib versus sunitinib (median, 14.2 versus 1.5 months). The results of this exploratory analysis suggest ctDNA sequencing may improve the prediction of the efficacy of single-drug therapies and support further evaluation of ripretinib in patients with KIT exon 11 + 17/18 mutations. ClinicalTrials.gov identifier: NCT03673501.

FDA-approved heterocyclic molecules for cancer treatment: Synthesis, dosage, mechanism of action and their adverse effect

As the incorporation of heterocycles increases the physical characteristics and biological activity of pharmacological molecules, heterocyclic scaffolds are commonly discovered as common cores in a wide spectrum of biologically active drugs. In the contemporary context, many heterocycles have arisen, playing vital roles in diverse pharmaceutical compounds that benefit humanity. Over 85 % of FDA-approved medication molecules contain heterocycles, and most importantly, numerous heterocyclic medicinal molecules indicate potential benefits against a range: of malignancies. The unique flexibility and dynamic core scaffold of these compounds have aided anticancer research. These medications are used to treat cancer patients by targeting particular genes, enzymes, and receptors. Aside from the drugs that are now on the market, numerous forms are being researched for their potential anti-cancer activity. Here in this review, we classified some molecules and biologically active heterocycles containing anticancer medicinal moieties approved by the FDA between 2019 and 2021 based on their use in various forms of cancer. We will focus on those that are suitable for cancer treatment, as well as the essential biochemical mechanisms of action, biological targets, synthetic methods, and inherent limiting considerations in their use.

Avapritinib-based SAR studies unveil a binding pocket in KIT and PDGFRA

Avapritinib is the only potent and selective inhibitor approved for the treatment of D842V-mutant gastrointestinal stromal tumors (GIST), the most common primary mutation of the platelet-derived growth factor receptor α (PDGFRA). The approval was based on the NAVIGATOR trial, which revealed overall response rates of more than 90%. Despite this transformational activity, patients eventually progress, mostly due to acquired resistance mutations or following discontinuation due to neuro-cognitive side effects. These patients have no therapeutic alternative and face a dismal prognosis. Notable, little is known about this drug's binding mode and its medicinal chemistry development, which is instrumental for the development of the next generation of drugs. Against this background, we solve the crystal structures of avapritinib in complex with wild-type and mutant PDGFRA and stem cell factor receptor (KIT), which provide evidence and understanding of inhibitor binding and lead to the identification of a sub-pocket (Gα-pocket). We utilize this information to design, synthesize and characterize avapritinib derivatives for the determination of key pharmacophoric features to overcome drug resistance and limit potential blood-brain barrier penetration.

Drugs in the GIST Field (Therapeutic Targets and Clinical Trial Staging)

BACKGROUND

Molecular targeted therapies are the most important type of medical treatment for GIST, but the development of GIST drugs and their targets have not been summarized.

METHODS

Drugs in the field of GIST were analyzed and collated through Pharmaprojects, ClinicalTrials. gov and PharmaGO databases.

RESULTS

As of 2021, there are 75 drugs that have appeared in the GIST clinical trials. The six most frequent targets in GIST clinical trials, in descending order of frequency, were KIT, PDGFRA, KDR (VEGFR2), FLT3, FLT1 (VEGFR1), and FLT4/VEGFR3. Only 8 drugs are in preclinical research. There are challenges in the development of new drugs for GIST.

CONCLUSION

This article analyzes and summarizes the general situation of GIST drugs, the target distribution of GIST drugs, and the trends in GIST drug-related clinical trials.

Efficacy and safety of ripretinib vs. sunitinib in patients with advanced gastrointestinal stromal tumor previously treated with imatinib: A phase 2, multicenter, randomized, open-label study in China

AIM

A bridging study of INTRIGUE study to assess the efficacy and safety of ripretinib versus sunitinib as second-line treatment in Chinese GIST patients.

METHODS

This was a phase 2, multicenter, randomized, open-label study in China. GIST patients previously treated with imatinib were randomized (1:1) to receive ripretinib 150 mg once daily (QD) by continuous dosing in 42-day cycles or sunitinib 50 mg QD in 42-day cycles (four weeks on/two weeks off). Primary endpoint was progression-free survival (PFS) by independent radiological review (IRR).

RESULTS

Between 6 December 2020 and 15 September 2021, 108 patients were randomized to receive ripretinib (n = 54) or sunitinib (n = 54) (all-patient [AP] intention-to-treat [ITT] population). Seventy patients had primary KIT exon 11 mutations (ripretinib, n = 35; sunitinib, n = 35; Ex11 ITT population). By data cut-off (20 July 2022), in AP ITT population, PFS by IRR was comparable between ripretinib and sunitinib arms (HR 0·99, 95 % CI 0·57, 1·69; nominal p = 0·92; median PFS [mPFS] 10·3 vs 8·3 months). In Ex11 ITT population, PFS by IRR was longer for ripretinib than sunitinib (HR 0·46, 95 % CI 0·23, 0·92; nominal p = 0·03; mPFS not reached in ripretinib arm and 4·9 months in sunitinib arm). Fewer patients experienced grade 3/4 treatment-related treatment-emergent adverse events with ripretinib (17%) versus sunitinib (56%).

CONCLUSIONS

Ripretinib demonstrated similar efficacy and a favorable safety profile versus sunitinib as second-line treatment in Chinese GIST patients. Furthermore, ripretinib provided greater clinically meaningful benefit versus sunitinib in patients with KIT exon 11 mutation.

An Expedition on Synthetic Methodology of FDA-approved Anticancer Drugs (2018-2021)

New drugs being established in the market every year produce specified structures for selective biological targeting. With medicinal insights into molecular recognition, these begot molecules open new rooms for designing potential new drug molecules. In this review, we report the compilation and analysis of a total of 56 drugs including 33 organic small molecules (Mobocertinib, Infigratinib, Sotorasib, Trilaciclib, Umbralisib, Tepotinib, Relugolix, Pralsetinib, Decitabine, Ripretinib, Selpercatinib, Capmatinib, Pemigatinib, Tucatinib, Selumetinib, Tazemetostat, Avapritinib, Zanubrutinib, Entrectinib, Pexidartinib, Darolutamide, Selinexor, Alpelisib, Erdafitinib, Gilteritinib, Larotrectinib, Glasdegib, Lorlatinib, Talazoparib, Dacomitinib, Duvelisib, Ivosidenib, Apalutamide), 6 metal complexes (Edotreotide Gallium Ga-68, fluoroestradiol F-18, Cu 64 dotatate, Gallium 68 PSMA-11, Piflufolastat F-18, 177Lu (lutetium)), 16 macromolecules as monoclonal antibody conjugates (Brentuximabvedotin, Amivantamab-vmjw, Loncastuximabtesirine, Dostarlimab, Margetuximab, Naxitamab, Belantamabmafodotin, Tafasitamab, Inebilizumab, SacituzumabGovitecan, Isatuximab, Trastuzumab, Enfortumabvedotin, Polatuzumab, Cemiplimab, Mogamulizumab) and 1 peptide enzyme (Erwiniachrysanthemi-derived asparaginase) approved by the U.S. FDA between 2018 to 2021. These drugs act as anticancer agents against various cancer types, especially non-small cell lung, lymphoma, breast, prostate, multiple myeloma, neuroendocrine tumor, cervical, bladder, cholangiocarcinoma, myeloid leukemia, gastrointestinal, neuroblastoma, thyroid, epithelioid and cutaneous squamous cell carcinoma. The review comprises the key structural features, approval times, target selectivity, mechanisms of action, therapeutic indication, formulations, and possible synthetic approaches of these approved drugs. These crucial details will benefit the scientific community for futuristic new developments in this arena.

Major adverse cardiovascular events of vascular endothelial growth factor tyrosine kinase inhibitors among patients with different malignancy: A systemic review and network meta-analysis

BACKGROUND

Vascular endothelial growth factor tyrosine kinase inhibitors (VEGF-TKIs) are a common cancer treatment. However, the pharmacologic characteristics of VEGF-TKIs may influence cardiovascular risks. The relative risks of major adverse cardiovascular events (MACEs) associated with VEGF-TKIs are poorly understood.

METHODS

We searched PubMed, Embase, and ClinicalTrials.gov from inception until August 31, 2021, for phase II/III randomized controlled trials of 11 VEGF-TKIs (axitinib, cabozantinib, lenvatinib, pazopanib, ponatinib, ripretinib, regorafenib, sorafenib, sunitinib, tivozanib, and vandetanib). The endpoints were heart failure, thromboembolism, and cardiovascular death. The Mantel-Haenszel method was used to calculate the risk of VEGF-TKI among users by comparing it to nonusers. Pairwise meta-analyses with a random-effects model were used to estimate the risks of the various VEGF-TKIs. We estimated ranked probability with a P-score and assessed credibility using the Confidence in Network Meta-Analysis framework.

RESULTS

We identified 69 trials involving 30 180 patients with cancer. The highest risk of MACEs was associated with high-potency tivazonib (odds ratio [OR]: 3.34), lenvatinib (OR: 3.26), and axitinib (OR: 2.04), followed by low-potency pazopanib (OR: 1.79), sorafenib (OR: 1.77), and sunitinib (OR: 1.66). The risk of heart failure significantly increased in association with less-selective sorafenib (OR: 3.53), pazopanib (OR: 3.10), and sunitinib (OR: 2.65). The risk of thromboembolism significantly increased in association with nonselective lenvatinib (OR: 3.12), sorafenib (OR: 1.54), and sunitinib (OR: 1.53). Higher potency (tivozanib, axitinib) and lower selectivity (sorafenib, vandetanib, pazopanib, sunitinib) were associated with a higher probability of heart failure. Low selectivity (lenvatinib, cabozantinib, sorafenib, sunitinib) was associated with a higher probability of thromboembolism.

CONCLUSION

Higher-potency and lower-selectivity VEGF-TKIs may influence the risks of MACEs, heart failure, and thromboembolism. These findings may facilitate evidence-based decision-making in clinical practice.

Unlocking the synthetic approaches and clinical application of approved small-molecule drugs for gastrointestinal cancer treatment: A comprehensive exploration

Gastrointestinal (GI) cancers encompass a group of malignancies affecting the digestive system, including the stomach, esophagus, liver, colon, rectum and pancreas. These cancers represent a significant global health burden, necessitating effective treatment strategies. Small-molecule drugs have emerged as crucial therapeutic options in the fight against GI cancers due to their oral bioavailability, targeted mechanisms of action, and well-established safety profiles. The review then elucidates the clinical applications and synthetic methods of clinically approved small-molecule drugs for the treatment of GI cancer, shedding light on their mechanisms of action and their potential in mitigating GI cancer progression. The review also discusses future prospects and the evolving landscape of small-molecule drug development in GI oncology, highlighting the potential for personalized medicine. In summary, this review provides valuable insights into cutting-edge strategies for harnessing clinically approved small-molecule drugs to combat GI cancer effectively.

Discovery of New Anti-Cancer Agents against Patient-Derived Sorafenib-Resistant Papillary Thyroid Cancer

Thyroid cancer is the most well-known type of endocrine cancer that is easily treatable and can be completely cured in most cases. Nonetheless, anti-cancer drug-resistant metastasis or recurrence may occur and lead to the failure of cancer therapy, which eventually leads to the death of a patient with cancer. This study aimed to detect novel thyroid cancer target candidates based on validating and identifying one of many anti-cancer drug-resistant targets in patient-derived sorafenib-resistant papillary thyroid cancer (PTC). We focused on targeting the sarco/endoplasmic reticulum calcium ATPase (SERCA) in patient-derived sorafenib-resistant PTC cells compared with patient-derived sorafenib-sensitive PTC cells. We discovered novel SERCA inhibitors (candidates 33 and 36) by virtual screening. These candidates are novel SERCA inhibitors that lead to remarkable tumor shrinkage in a xenograft tumor model of sorafenib-resistant patient-derived PTC cells. These results are clinically valuable for the progression of novel combinatorial strategies that facultatively and efficiently target extremely malignant cancer cells, such as anti-cancer drug-resistant PTC cells.

Repurposing Synthetic Congeners of a Natural Product Aurone Unveils a Lead Antitumor Agent Inhibiting Folded P-Loop Conformation of MET Receptor Tyrosine Kinase

A library of 24 congeners of the natural product sulfuretin were evaluated against nine panels representing nine cancer diseases. While sulfuretin elicited very weak activities at 10 µM concentration, congener 1t was identified as a potential compound triggering growth inhibition of diverse cell lines. Mechanistic studies in HCT116 colon cancer cells revealed that congener 1t dose-dependently increased levels of cleaved-caspases 8 and 9 and cleaved-PARP, while it concentration-dependently decreased levels of CDK4, CDK6, Cdc25A, and Cyclin D and E resulting in induction of cell cycle arrest and apoptosis in colon cancer HCT116 cells. Mechanistic study also presented MET receptor tyrosine kinase as the molecular target mediating the anticancer activity of compound 1t in HCT116 cells. In silico study predicted folded p-loop conformation as the form of MET receptor tyrosine kinase responsible for binding of compound 1t. Together, the current study presents compound 1t as an interesting anticancer lead for further development.

c-Kit Receptors as a Therapeutic Target in Cancer: Current Insights

c-Kit is a type III receptor tyrosine kinase (RTK) that has an essential role in various biological functions including gametogenesis, melanogenesis, hematopoiesis, cell survival, and apoptosis. c-KIT aberrations, either overexpression or loss-of-function mutations, have been implicated in the pathogenesis and development of many cancers, including gastrointestinal stromal tumors, mastocytosis, acute myeloid leukemia, breast, thyroid, and colorectal cancer, making c-KIT an attractive molecular target for the treatment of cancers. Therefore, a lot of effort has been put into investigating the utility of tyrosine kinase inhibitors for the management of c-KIT mutated tumors. This review of the literature illustrates the role of c-KIT mutations in many cancers, aiming to provide insights into the role of TKIs as a therapeutic option for cancer patients with c-KIT aberrations. In conclusion, c-KIT is implicated in different types of cancer, and it could be a successful molecular target; however, proper detection of the underlying mutation type is required before starting the appropriate personalized therapy.

Multi-disciplinary management of recurrent gastrointestinal stromal tumor harboring KIT exon 11 mutation with the switch-control kinase inhibitor ripretinib and surgery

Ripretinib is a tyrosine kinase inhibitor that was approved by the United States FDA in 2020 for treatment of advanced gastrointestinal stromal tumor (GIST) in patients who received prior treatment with three or more tyrosine kinase inhibitors. In this case report, we show the durable clinical benefit achieved in a patient with GIST by using ripretinib and repeated timely surgical resection of limited disease progression. The total time on ripretinib was 43 months which is longer than the current reported data from ripretinib clinical trials. Such approach for using multi-disciplinary disease management can improve the durability of response to tyrosine kinase inhibitors, including ripretinib, and associated clinical outcomes.

Ripretinib for the treatment of advanced, imatinib-resistant gastrointestinal stromal tumors

Discovery of constitutive activation of KIT/PDGFRA tyrosine kinases in gastrointestinal stromal tumors (GISTs) leads to the development of the targeted drug imatinib. However, the inevitable development of imatinib resistance remains a major issue. Ripretinib is a novel targeted drug that inhibits the activities of a broad spectrum of drug-resistant KIT/PDGFRA mutants. It was approved in 2020 and is currently recommended by major international guidelines as the fourth-line and beyond therapy for advanced GISTs. Emerging evidence shows that ripretinib is superior to sunitinib as a second-line treatment for KIT exon 11-mutated GISTs due to its activity against highly heterogeneous frequently occurring secondary mutations. This review summarizes current data on the use of ripretinib to treat advanced imatinib-resistant GISTs. We also propose future research directions to improve the targeted GIST treatment.

Large-Scale, Multicenter, Prospective Registry Study of Ripretinib in Advanced GIST: A Real-World Study from China

INTRODUCTION

Tyrosine-kinase inhibitors (TKIs) have become the standard treatment for patients with advanced gastrointestinal stromal tumor (GIST); however, secondary mutations can still drive disease progression. Studies have shown that ripretinib, a novel switch-control TKI, inhibits various primary and secondary drug-resistant mutations. There is a paucity of data on the effectiveness and safety of ripretinib in a real-world setting. This prospective, large-scale, real-world registry study aimed to evaluate the effectiveness and safety of ripretinib as a fourth-line treatment in Chinese patients with advanced GIST.

METHODS

Patients ≥ 18 years of age having recurrent/metastatic GIST were enrolled. Key endpoints were median progression-free survival (mPFS), median overall survival (mOS), and adverse events (AEs) incidence. Univariate and multivariate analyses were conducted to identify various parameters associated with PFS.

RESULTS

A total of 240 patients were enrolled. After a median follow-up period of 6.5 months, the mPFS [95% confidence interval (CI)] was 7.70 (6.60, 8.60) months and the mOS was not reached. Multivariate analysis revealed association of Eastern Cooperative Oncology Group (ECOG) performance status score with PFS and superior benefits for non-gastric was observed as compared to gastric GISTs [hazard ratio (HR) 0.58, 95% CI (0.39-0.86)]. Disease control rate and tumor shrinkage (any magnitude) was 73% and 43%, respectively. Ripretinib was also effective in the subgroup of patients with different gene mutations. The toxicities were tolerable, and most reported AEs were alopecia (17.1%) and hand-foot syndrome (15.4%).

CONCLUSION

Ripretinib demonstrated effectiveness and a tolerable safety profile, making it a viable option as a fourth- or later-line treatment in Chinese patients with advanced GISTs, especially for non-gastric GISTs.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT05697107.

Evaluation of Systemic Treatment Options for Gastrointestinal Stromal Tumours

Gastrointestinal stromal tumours (GIST) are the most common mesenchymal tumours of the gastrointestinal tract. Surgical treatment is recommended for the majority of localised GIST, while systemic treatment is the cornerstone of management for metastatic or unresectable disease. While a three-year regimen of imatinib is the standard of care in the adjuvant setting, there is no precise recommendation for the duration of neoadjuvant treatment, where imatinib is usually given between 4 and 12 months. Continuous treatment with imatinib at a dose of 400 mg once per day is recommended for most patients with unresectable or metastatic GIST in the first line. An exception is represented by patients with tumours harbouring the imatinib-insensitive PDGFRA D842V mutation who would be better treated with avapritinib. Targeted therapies are also recommended in the presence of NTRK rearrangements and BRAF mutations, although limited data are available. While an increase in the dose of imatinib to 800 mg is an option for the second line, sunitinib is usually considered the standard of care. Similar outcomes were reported for ripretinib in patients with tumours harbouring KIT exon 11 mutation, with significantly fewer side effects. Regorafenib and ripretinib are the standards of care in the third and fourth lines, respectively. The recent development of various systemic treatment options allows for a more personalised approach based on the molecular profile of the GIST, patient characteristics, and the profile of medications' adverse events. A multidisciplinary approach is paramount since combining systemic treatment with locoregional treatment options and supportive care is vital for long-term survival.

Advances in protein kinase drug discovery through targeting gatekeeper mutations

INTRODUCTION

Acquired resistance caused by gatekeeper mutations has become a major challenge for approved kinase inhibitors used in the clinic. Consequently, the development of new-generation inhibitors or degraders to overcome clinical resistance has become an important research focus for the field.

AREAS COVERED

This review summarizes the common gatekeeper mutations in druggable kinases and the constantly evolving inhibitors or degraders designed to overcome single or double mutations of gatekeeper residues. Furthermore, the authors provide their perspectives on the medicinal chemistry strategies for addressing clinical resistance with gatekeeper mutations.

EXPERT OPINION

The authors suggest optimizing kinase inhibitors to interact effectively with gatekeeper residues, altering the binding mode or binding pocket to avoid steric clashes, improving binding affinity with the target, utilizing protein degraders, and developing combination therapy. These approaches have the potential to be effective in overcoming resistance due to gatekeeper residues.

Molecular Advances in the Treatment of Advanced Gastrointestinal Stromal Tumor

Most gastrointestinal stromal tumors (GIST) are driven by activating mutations in Proto-oncogene c-KIT (KIT) or PDGFRA receptor tyrosine kinases (RTK). The emergence of effective therapies targeting these mutations has revolutionized the management of advanced GIST. 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. Moreover, some patients have de novo resistance to imatinib, such as those with mutations in PDGFRA exon 18 or those without KIT or PDGFRA mutation. 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.

The multifaceted landscape behind imatinib resistance in gastrointestinal stromal tumors (GISTs): A lesson from ripretinib

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal sarcomas and the gold-standard treatment is represented by tyrosine kinase inhibitors (TKIs). Unfortunately, first-line treatment with the TKI imatinib usually promotes partial response or stable disease rather than a complete response, and resistance appears in most patients. Adaptive mechanisms are immediately relevant at the beginning of imatinib therapy, and they may represent the reason behind the low complete response rates observed in GISTs. Concurrently, resistant subclones can silently continue to grow or emerge de novo, becoming the most representative populations. Therefore, a slow evolution of the primary tumor gradually occurs during imatinib treatment, enriching heterogeneous imatinib resistant clonal subpopulations. The identification of secondary KIT/PDGFRA mutations in resistant GISTs prompted the development of novel multi-targeted TKIs, leading to the approval of sunitinib, regorafenib, and ripretinib. Although ripretinib has broad anti-KIT and -PDGFRA activity, it failed to overcome sunitinib as second-line treatment, suggesting that imatinib resistance is more multifaceted than initially thought. The present review summarizes several biological aspects suggesting that heterogeneous adaptive and resistance mechanisms can also be driven by KIT or PDGFRA downstream mediators, alternative kinases, as well as ncRNAs, which are not targeted by any TKI, including ripretinib. This may explain the modest effect observed with ripretinib and all anti-GIST agents in patients.

Ripretinib in combination with tyrosine kinase inhibitor as a late-line treatment option for refractory gastrointestinal stromal tumors: two case reports and literature review

Background: This case report presents two clinical cases of metastatic refractory gastrointestinal stromal tumor (GIST) with treatment history of 6-14 years. The follow-up treatment of both cases comprised ripretinib dose escalation and its combination with other tyrosine kinase inhibitors (TKIs). To the best of our knowledge, this is the first report that explored ripretinib combination therapy in the late-line treatment of GISTs. Case description: Case-1 represents a 57-year-old female patient who underwent surgical resection for retroperitoneal GIST in 2008. After tumor recurrence in 2009, imatinib was started with complete response for 8 years. Imatinib was followed by sunitinib and regorafenib treatment. In March 2021, due to progressive disease (PD), the patient started ripretinib (150 mg QD) and achieved partial response (PR). Six months later, the patient showed PD. Subsequently, ripretinib dose was increased (150 mg BID) followed by ripretinib (100 mg QD) and imatinib (200 mg QD) combination. CT performed in February 2022 revealed stable lesions with internal visible necrosis. Combination therapy achieved stable disease (SD) for 7 months. On further follow-up in July 2022, the patient showed PD and died in September 2022. Case-2: represents a 73-year-old female patient diagnosed with unresectable duodenal GIST with liver, lung, and lymph node metastases in 2016. After treatment with imatinib, followed by sunitinib, regorafenib, and imatinib rechallenge, ripretinib (150 mg QD) was administered in May 2021, and SD was achieved. Ripretinib dose was increased (200 mg QD) due to PD in December 2021. The tumor showed heterogeneous manifestations, with overall size increase and regression in right posterior lobe. In February 2022, ripretinib (150 mg) plus sunitinib (25 mg) QD was commenced. On follow-up in April 2022, the patient showed slightly improved symptoms with stable hematologic parameters. Combination therapy achieved SD for 5 months and the patient showed PD in July 2022 and discontinued the treatment later. The patient was in poor general condition and was receiving nutritional therapy until last follow-up in October 2022. Conclusion: This case report provides evidence that combination therapy of ripretinib with other TKIs could be an effective late-line treatment option for refractory GIST patients.

Efficacy and safety of ripretinib in Chinese patients with advanced gastrointestinal stromal tumors: a real-world, multicenter, observational study

Introduction

Mutations in KIT proto-oncogene, receptor tyrosine kinase (KIT) and platelet-derived growth factor receptor-α (PDGFRA) render the available tyrosine kinase inhibitors (TKI) ineffective in treating advanced gastrointestinal stromal tumors (GIST). Ripretinib, a broad-spectrum switch-control kinase inhibitor, has shown increased efficacy and manageable safety, but real-world evidence remains scarce. This study evaluates the efficacy and safety of ripretinib among Chinese patients in a real-world setting.

Methods

Advanced GIST patients (N=23) receiving ripretinib following progression on previous lines of TKI treatment were enrolled to determine the efficacy [progression-free survival (PFS) and overall survival (OS)]. Safety was assessed by the incidence and severity of adverse events (AEs). All statistical analyses were performed using SPSS version 20.0 and a p-value of <0.05 was considered significant.

Results

The median PFS (mPFS) of efficacy analysis set (EAS) (N=21) was 7.1 months. mPFS of patients receiving ripretinib following ≤2 lines of previous TKI treatment and ≥3 prior lines of therapy were 7.1 and 9.2 months, respectively. The median OS (mOS) was 12.0 months and shorter interval between the end of the latest TKI and ripretinib therapy was correlated with longer median PFS and OS (p=0.054 and p=0.046), respectively. Alopecia and asthenia were the most common AEs observed.

Conclusion

Compared to previous lines of TKI in advanced GIST patients, ripretinib showed superior efficacy with clinically manageable AEs. Real-world results are comparable to that of phase III INVICTUS study and its Chinese bridging study. Hence, ripretinib can be used for the clinical management of advanced GIST patients.

Efficacy of post-first-line agents for advanced gastrointestinal stromal tumors following imatinib failure: A network meta-analysis

BACKGROUND

Imatinib is the standard first-line treatment for advanced gastrointestinal stromal tumors (GISTs); however, most patients eventually develop imatinib resistance, leading to considerable clinical challenges. Few direct comparisons have been made between different post-first-line therapies on clinical efficacy in advanced GIST following imatinib failure.

METHODS

Databases including PubMed, Embase, Scopus, Google Scholars, and Cochrane Library from inception to February 2023 were retrieved for randomized controlled trials evaluating the clinical efficacy of different post-first-line agents for advanced GIST following imatinib failure. Network and conventional meta-analysis were carried out using Stata/MP 16.0.

RESULTS

Ripretinib showed significant improvement in progression-free survival (PFS) rates from the 2nd to the 12th month compared to placebo, while there was virtually no evidence that the rest active agents had a significant benefit at the 12th month. Masitinib, ripretinib, sunitinib, regorafenib, and pimitespib exhibited significantly longer median PFS than placebo, and pairwise comparisons indicated there were no significant differences among masitinib, ripretinib, and sunitinib. These post-first-line agents decreased the risk of disease progression or death by 65% (HR = 0.35, 95% CI: 0.26-0.47) compared to placebo. Ripretinib and sunitinib came into effect earlier and exhibited more consistent overall survival (OS) rate improvements than masitinib and pimitespib, while pairwise comparisons revealed no significant differences in these four active agents concerning the improvement in OS rate. These post-first-line agents decreased the risk of death by 39% (HR = 0.61, 95% CI: 0.44-0.83) over placebo for advanced GIST following imatinib failure.

CONCLUSION

The active agents in our analysis as post-first-line therapies are able to provide superior clinical efficacy, with improved PFS rate and OS rate at certain time points, as well as absolute values of PFS and OS for advanced GIST. Ripretinib might be the optimal recommendation as a post-first-line treatment for advanced GIST following imatinib failure.

Advances in immunology and immunotherapy for mesenchymal gastrointestinal cancers

Mesenchymal gastrointestinal cancers are represented by the gastrointestinal stromal tumors (GISTs) which occur throughout the whole gastrointestinal tract, and affect human health and economy globally. Curative surgical resections and tyrosine kinase inhibitors (TKIs) are the main managements for localized GISTs and recurrent/metastatic GISTs, respectively. Despite multi-lines of TKIs treatments prolonged the survival time of recurrent/metastatic GISTs by delaying the relapse and metastasis of the tumor, drug resistance developed quickly and inevitably, and became the huge obstacle for stopping disease progression. Immunotherapy, which is typically represented by immune checkpoint inhibitors (ICIs), has achieved great success in several solid tumors by reactivating the host immune system, and been proposed as an alternative choice for GIST treatment. Substantial efforts have been devoted to the research of immunology and immunotherapy for GIST, and great achievements have been made. Generally, the intratumoral immune cell level and the immune-related gene expressions are influenced by metastasis status, anatomical locations, driver gene mutations of the tumor, and modulated by imatinib therapy. Systemic inflammatory biomarkers are regarded as prognostic indicators of GIST and closely associated with its clinicopathological features. The efficacy of immunotherapy strategies for GIST has been widely explored in pre-clinical cell and mouse models and clinical experiments in human, and some patients did benefit from ICIs. This review comprehensively summarizes the up-to-date advancements of immunology, immunotherapy and research models for GIST, and provides new insights and perspectives for future studies.

Anti-Cancer SERCA Inhibitors Targeting Sorafenib-Resistant Human Papillary Thyroid Carcinoma

Thyroid cancer is generally curable and, in many cases, can be completely treated, although it can sometimes recur after cancer therapy. Papillary thyroid cancer (PTC) is known as one of the most general subtypes of thyroid cancer, which take up nearly 80% of whole thyroid cancer. However, PTC may develop anti-cancer drug resistance via metastasis or recurrence, making it practically incurable. In this study, we propose a clinical approach that identifies novel candidates based on target identification and validation of numerous survival-involved genes in human sorafenib-sensitive and -resistant PTC. Consequently, we recognized a sarco/endoplasmic reticulum calcium ATPase (SERCA) in human sorafenib-resistant PTC cells. Based on the present results, we detected novel SERCA inhibitor candidates 24 and 31 via virtual screening. These SERCA inhibitors showed remarkable tumor shrinkage in the sorafenib-resistant human PTC xenograft tumor model. These consequences would be clinically worthwhile for the development of a new combinatorial strategy that effectively targets incredibly refractory cancer cells, such as cancer stem cells and anti-cancer drug-resistant cells.

Emerging Targeted Therapeutic Strategies to Overcome Imatinib Resistance of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common malignant mesenchymal neoplasms of the gastrointestinal tract. The gold standard for the diagnosis of GISTs is morphologic analysis with an immunohistochemical evaluation plus genomic profiling to assess the mutational status of lesions. The majority of GISTs are driven by gain-of-function mutations in the proto-oncogene c-KIT encoding the tyrosine kinase receptor (TKR) known as KIT and in the platelet-derived growth factor-alpha receptor (PDGFRA) genes. Approved therapeutics are orally available as tyrosine kinase inhibitors (TKIs) targeting KIT and/or PDGFRA oncogenic activation. Among these, imatinib has changed the management of patients with unresectable or metastatic GISTs, improving their survival time and delaying disease progression. Nevertheless, the majority of patients with GISTs experience disease progression after 2-3 years of imatinib therapy due to the development of secondary KIT mutations. Today, based on the identification of new driving oncogenic mutations, targeted therapy and precision medicine are regarded as the new frontiers for GISTs. This article reviews the most important mutations in GISTs and highlights their importance in the current understanding and treatment options of GISTs, with an emphasis on the most recent clinical trials.

Top advances of the year: Precision oncology

The advent of precision medicine has changed the landscape of oncologic biomarkers, drug discovery, drug development, and, more importantly, outcomes for patients with cancer. Precision oncology entails the genomic profiling of tumors to detect actionable aberrations. The advances in clinical next-generation sequencing from both tumor tissue and liquid biopsy and availability of targeted therapies has rapidly entered mainstream clinical practice. In this review, recent major developments in precision oncology that have affected outcomes for patients with cancer are discussed. Rapid clinical development was seen of targeted agents across various mutational profiles such as KRASG12C (which was considered "undruggable" for almost 4 decades), Exon 20 insertions, and RET mutations. Approaches to precision chemotherapy delivery by the introduction of antibody drug conjugates in the armamentarium against lung cancer has been appreciated.

Evaluating the impact of co-administered drug and disease on ripretinib exposure: A physiologically-based pharmacokinetic modeling approach

Ripretinib, as an oral kinase inhibitor, has been approved to treat advanced gastrointestinal stromal tumors (GIST) and is often used in combination with other drugs to slow disease progression, thus potential drug-drug Interactions (DDIs) and drug-disease interactions (DDZIs) have received much attention. To guide clinical rational drug use, this study assessed the effect of co-administered drugs and diseases on ripretinib exposure. Simcyp® Simulator was used to develop the physiologically-based pharmacokinetic (PBPK) model of ripretinib, which was validated and refined with clinical data. We then examined the impact of several CYP3A4 inhibitors and inducers as well as different diseases on ripretinib exposure using the validated model. In the DDI simulation, moderate CYP3A4 inhibitors and inducers changed the exposure of ripretinib by 1.25-2 fold. In hepatic impairment (HI), the simulation showed that ripretinib's AUC increased by 32%, 100%, and 152% for Child-Pugh A, B, and C classification while C_max increased by 2%, 10%, and 15%, respectively. In renal impairment (RI), the model-simulated AUC in moderate and severe RIs increased by 27% and 20%. In conclusion, PBPK models demonstrated quantitative prediction of ripretinib's pharmacokinetic changes under varying conditions that might be useful for its rational use.

Activity of Anlotinib in the Second-Line Therapy of Metastatic Gastrointestinal Stromal Tumors: A Prospective, Multicenter, In Vitro Study

BACKGROUND

Anlotinib is a multi-target tyrosine kinase inhibitor that can effectively inhibit tumor cell proliferation after receptor kinase activation caused by KIT gene mutation.

METHODS

We tested the inhibitory effect of anlotinib in GIST cell lines with different gene mutations and evaluated the efficacy of anlotinib for patients with metastatic GIST after imatinib failure in a multicenter, single-arm, phase II study.

RESULTS

In vitro, V654A mutation encoded by KIT exon 13 was intermediately sensitive to anlotinib. Moreover, anlotinib was able to partly suppress the activation loop mutation D820A from exon 17 while another activation loop mutation N822K, also from exon 17, was resistant to anlotinib. From September 2018 to October 2020, 64 patients from 9 Chinese medical centers were enrolled in this study. Seven patients had partial response and 39 patients had stable disease. The median PFS was 8.0 months. There was no statistical significance comparing with PFS of sunitinib second-line therapy at the same period. The most common adverse events related to anlotinib treatment were hypertension, neutropenia, and fatigue.

CONCLUSION

Anlotinib showed moderate antitumor activity in drug-resistant GIST cell lines in vitro, and good PFS and better tolerance in second-line therapy study.

Emerging Data on the Safety and Efficacy of Ripretinib for the Treatment of Gastrointestinal Stromal Tumors

In patients with gastrointestinal stromal tumors (GIST), systemic treatment after disease progression on imatinib is challenging. Sunitinib and regorafenib are approved in the second- and third-line setting, respectively, with activity against certain secondary mutations with comparatively much lower response rates and survival increment compared to imatinib. All three of these drugs were serendipitously found to have activity in GIST, starting with imatinib, which was formulated for its ability to inhibit BCR-ABL in chronic myelogenous leukemia. Ripretinib is a drug that was specifically developed as a more potent KIT tyrosine kinase inhibitor (TKI), with broad-spectrum activity against the mutations encountered in GIST. Encouraging responses in early and later lines of treatment in the Phase 1 trial of ripretinib in GIST led to the rapid development of this novel drug. In a Phase 3 randomized clinical trial with cross-over, ripretinib demonstrated superior PFS and overall survival (OS) in 4th-line treatment and beyond compared to placebo. This established 150 mg once daily ripretinib as the standard of care in this setting. Ripretinib is generally well tolerated, with common adverse effects of hair loss, diarrhea, cramps, fatigue and nausea. The favorable safety profile and efficacy of ripretinib prompted its evaluation in a randomized phase 3 trial in the 2nd-line treatment setting. However, it did not result in a longer PFS duration than sunitinib. Although the efficacy of ripretinib in this unselected patient population was not significantly different from that of sunitinib, the tolerability profile was better. This review article aims to review the efficacy and tolerability profile of ripretinib, together with its role in the setting of unresectable or metastatic GIST.

Combination of pimitespib (TAS-116) with sunitinib is an effective therapy for imatinib-resistant gastrointestinal stromal tumors

Despite the effectiveness of imatinib, most gastrointestinal stromal tumors (GISTs) develop resistance to the treatment, mainly due to the reactivation of KIT tyrosine kinase activity. Sunitinib, which inhibits the phosphorylation of KIT and vascular endothelial growth factor (VEGF) receptor, has been established as second-line therapy for GISTs. The recently-developed heat shock protein 90 (HSP90) inhibitor pimitespib (PIM; TAS-116) demonstrated clinical benefits in some clinical trials; however, the effects were limited. The aim of our study was therefore to clarify the effectiveness and mechanism of the combination of PIM with sunitinib for imatinib-resistant GISTs. We evaluated the efficacy and mechanism of the combination of PIM with sunitinib against imatinib-resistant GIST using imatinib-resistant GIST cell lines and murine xenograft models. In vitro analysis demonstrated that PIM and sunitinib combination therapy strongly inhibited growth and induced apoptosis in imatinib-resistant GIST cell lines by inhibiting KIT signaling and decreasing auto-phosphorylated KIT in the Golgi apparatus. In addition, PIM and sunitinib combination therapy enhanced antitumor responses in the murine xenograft models compared to individual therapies. Further analysis of the xenograft models showed that the combination therapy not only downregulated the KIT signaling pathway but also decreased the tumor microvessel density. Furthermore, we found that PIM suppressed VEGF expression in GIST cells by suppressing protein kinase D2 and hypoxia-inducible factor-1 alpha, which are both HSP90 client proteins. In conclusion, the combination of PIM and sunitinib is effective against imatinib-resistant GIST via the downregulation of KIT signaling and angiogenic signaling pathways.

Ripretinib for the treatment of adult patients with advanced gastrointestinal stromal tumors

INTRODUCTION

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. Imatinib mesylate revolutionized the management of advanced/metastatic GIST, and remains the standard first-line therapy in this setting. Upon development of secondary resistance, sunitinib and regorafenib are used as subsequent treatments, although clinical benefit is often non-durable. Ripretinib is a type II kinase inhibitor targeting KIT and PDGFRA mutations and resistance through switching active I and inactive II forms.

AREAS COVERED

This drug profile article provides an overview of the current state of the art treatment algorithm for advanced/metastatic GIST, focusing on the role of ripretinib in the fourth-line setting as defined by currently available clinical trials evidence. The mechanism of action, the safety profile, efficacy, and clinical application of ripretinib are presented. In addition, the Phase I study (NCT02571036) through which the optimal dose was established and the Phase III trials that assessed the efficacy and safety of ripretinib as fourth- (INVICTUS) and second-line treatment (INTRIGUE) are presented.

EXPERT OPINION

Ripretinib is a safe and an effective therapy for the fourth-line setting in advanced/metastatic GIST. Future studies should evaluate combination schedules and the identification of markers predictive of benefit from ripretinib.

Chinese Pedigree with Hereditary Gastrointestinal Stromal Tumors: A Case Report and Literature Review

Familial gastrointestinal stromal tumor (GIST) is a rare autosomal dominant genetic disorder with only a few affected families reported to date. Here, we report a case of familial GISTs harboring a novel germline mutation within exon 18 of KIT. A 58-year-old male patient presented with gastric subepithelial lesions accompanied by cutaneous hyperpigmentation, which were subsequently diagnosed as multinodular GISTs. Endoscopic surgery was initially conducted to remove the larger lesions, and pathological examinations were then conducted for the diagnosis of GISTs. Family history revealed that some other family members had similar cutaneous pigmentations. Whole-exome sequencing was used to search for potential driver mutations, and Sanger sequencing was used for mutation validation. A novel primary driver mutation of KIT (c.G2485C, p.A829P) was detected in these hereditary GISTs, which has been reported in some targeted chemotherapy-resistant GISTs. Cell models were subsequently established for the rapid screening of candidate drugs and exploring potential mechanisms. This mutation could lead to cell proliferation and imatinib resistance by ligand-independent activation of KIT; however, ripretinib administration was identified as an applicable targeted therapy for this mutation. The mutation activated the JAK/STAT3 and MAPK/ERK pathways, which could be inhibited by ripretinib administration. To the best of our knowledge, this is the first report of the KIT-A829P mutation in familial GISTs, complementing the pathogenesis of familial GISTs and providing valuable information for the precision treatment of this disease.

Targeting the Tumor-Tumor Microenvironment Crosstalk

INTRODUCTION

Cancer development and progression is a complex process influenced by co-evolution of the cancer cells and their microenvironment. However, traditional anti-cancer therapy is mostly targeted toward cancer cells. To improve the efficacy of cancer drugs, the complex interactions between the tumor (T) and the tumor microenvironment (TME) should be considered while developing therapeutics.

AREAS COVERED

The present review article will discuss the components of T-TME as well as the potential to co-target these two distinct elements. We document that these approaches have resulted in success in preventing tumor progression and metastasis, albeit in animal models in some cases. Lastly, it is important to consider the tissue context and tumor type as these could significantly modify the role of these molecules/pathways and hence the overall likelihood of response. Furthermore, we discuss the potential strategies to target the components of tumor microenvironment in anti-cancer therapy. PubMed and ClinicalTrials.gov was searched through May 2023.

EXPERT OPINION

The tumor-tumor microenvironment cross talk and heterogeneity are major mechanisms conferring resistance to standard of care. Better understanding of the tissue specific T-TME interactions and dual targeting has the promise of improving cancer control and clinical outcomes.

To Investigate Growth Factor Receptor Targets and Generate Cancer Targeting Inhibitors

Receptor tyrosine kinase (RTK) regulates multiple pathways, including Mitogenactivated protein kinases (MAPKs), PI3/AKT, JAK/STAT pathway, etc. which has a significant role in the progression and metastasis of tumor. As RTK activation regulates numerous essential bodily processes, including cell proliferation and division, RTK dysregulation has been identified in many types of cancers. Targeting RTK is a significant challenge in cancer due to the abnormal upregulation and downregulation of RTK receptors subfamily EGFR, FGFR, PDGFR, VEGFR, and HGFR in the progression of cancer, which is governed by multiple RTK receptor signalling pathways and impacts treatment response and disease progression. In this review, an extensive focus has been carried out on the normal and abnormal signalling pathways of EGFR, FGFR, PDGFR, VEGFR, and HGFR and their association with cancer initiation and progression. These are explored as potential therapeutic cancer targets and therefore, the inhibitors were evaluated alone and merged with additional therapies in clinical trials aimed at combating global cancer.

CRISPR/Cas9-engineering of HMC-1.2 cells renders a human mast cell line with a single D816V-KIT mutation: An improved preclinical model for research on mastocytosis

The HMC-1.2 human mast cell (huMC) line is often employed in the study of attributes of neoplastic huMCs as found in patients with mastocytosis and their sensitivity to interventional drugs in vitro and in vivo. HMC-1.2 cells express constitutively active KIT, an essential growth factor receptor for huMC survival and function, due to the presence of two oncogenic mutations (D816V and V560G). However, systemic mastocytosis is commonly associated with a single D816V-KIT mutation. The functional consequences of the coexisting KIT mutations in HMC-1.2 cells are unknown. We used CRISPR/Cas9-engineering to reverse the V560G mutation in HMC-1.2 cells, resulting in a subline (HMC-1.3) with a single mono-allelic D816V-KIT variant. Transcriptome analyses predicted reduced activity in pathways involved in survival, cell-to-cell adhesion, and neoplasia in HMC-1.3 compared to HMC-1.2 cells, with differences in expression of molecular components and cell surface markers. Consistently, subcutaneous inoculation of HMC-1.3 into mice produced significantly smaller tumors than HMC-1.2 cells, and in colony assays, HMC-1.3 formed less numerous and smaller colonies than HMC-1.2 cells. However, in liquid culture conditions, the growth of HMC-1.2 and HMC-1.3 cells was comparable. Phosphorylation levels of ERK1/2, AKT and STAT5, representing pathways associated with constitutive oncogenic KIT signaling, were also similar between HMC-1.2 and HMC-1.3 cells. Despite these similarities in liquid culture, survival of HMC-1.3 cells was diminished in response to various pharmacological inhibitors, including tyrosine kinase inhibitors used clinically for treatment of advanced systemic mastocytosis, and JAK2 and BCL2 inhibitors, making HMC-1.3 more susceptible to these drugs than HMC-1.2 cells. Our study thus reveals that the additional V560G-KIT oncogenic variant in HMC-1.2 cells modifies transcriptional programs induced by D816V-KIT, confers a survival advantage, alters sensitivity to interventional drugs, and increases the tumorigenicity, suggesting that engineered huMCs with a single D816V-KIT variant may represent an improved preclinical model for mastocytosis.

TKI Treatment Sequencing in Advanced Gastrointestinal Stromal Tumors

Prior to the early 2000s, patients with advanced gastrointestinal stromal tumors (GIST) had very poor prognoses owing to a lack of effective therapies. The development of tyrosine kinase inhibitors at the turn of the century significantly improved the overall survival for patients with GIST. The resounding success of imatinib in the first clinical trial of a tyrosine kinase inhibitor to treat GIST led to its approval for first-line therapy for advanced GIST; this study was open to all comers and not restricted to any GIST subtype(s). The trials that led to the approvals of second-, third-, and fourth-line therapy for advanced GIST were also open to all patients with advanced/metastatic GIST. Only in retrospect do we realize the role that the molecular subtypes played in the results observed in these studies. In this review, we discuss the studies that led to the US Food and Drug Administration approval of imatinib (first line), sunitinib (second line), regorafenib (third line), and ripretinib (fourth line) for advanced KIT-mutant GIST. In addition, we review how information about GIST molecular subtypes has been used to accelerate the approval of other targeted therapies for non-KIT mutant GIST, leading to the approval of five additional drugs indicated for the treatment of specific GIST molecular subtypes. We also discuss how our understanding of the molecular subtypes will play a role in the next generation of therapeutic approaches for treating advanced GIST.

Identification of Thiazolo[5,4-b]pyridine Derivatives as c-KIT Inhibitors for Overcoming Imatinib Resistance

c-KIT is a promising therapeutic target against gastrointestinal stromal tumor (GIST). In order to identify novel c-KIT inhibitors capable of overcoming imatinib resistance, we synthesized 31 novel thiazolo[5,4-b]pyridine derivatives and performed SAR studies. We observed that, among these substances, 6r is capable of inhibiting significantly c-KIT and suppressing substantially proliferation of GIST-T1 cancer cells. It is of note that 6r is potent against a c-KIT V560G/D816V double mutant resistant to imatinib. Compared with sunitinib, 6r possesses higher differential cytotoxicity on c-KIT D816V Ba/F3 cells relative to parental Ba/F3 cells. In addition, kinase panel profiling reveals that 6r has reasonable kinase selectivity. It was found that 6r remarkably attenuates proliferation of cancer cells via blockade of c-KIT downstream signaling, and induction of apoptosis and cell cycle arrest. Furthermore, 6r notably suppresses migration and invasion, as well as anchorage-independent growth of GIST-T1 cells. This study provides useful SAR information for the design of novel c-KIT inhibitors overcoming imatinib-resistance.

Patient-reported outcomes in individuals with advanced gastrointestinal stromal tumor treated with ripretinib in the fourth-line setting: analysis from the phase 3 INVICTUS trial

BACKGROUND

Ripretinib is a novel switch-control kinase inhibitor that inhibits KIT and PDGFRA signaling. In the INVICTUS phase 3 trial, ripretinib increased median progression-free survival and prolonged overall survival vs. placebo in ≥ fourth-line advanced GIST. Here, we report prespecified analysis of quality of life (QoL) as assessed by patient-reported outcome (PRO) measures and an exploratory analysis evaluating the impact of alopecia on QoL.

METHODS

In the INVICTUS trial (NCT03353753), QoL was assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30; physical function, role function, overall health, and overall QoL) and the EuroQoL 5-Dimension 5-Level (EQ-5D-5 L; visual analogue scale). Analysis of covariance (ANCOVA) models compared changes in scores from baseline to treatment cycle 2, day 1 within and between ripretinib and placebo. Within the ripretinib arm, repeated measures models assessed the impact of alopecia on QoL.

RESULTS

Patients receiving ripretinib maintained QoL (as assessed by the EORTC QLQ-C30 and EQ-5D-5 L PRO measures) from baseline to cycle 2, day 1 whereas QoL declined with placebo, resulting in clinically significant differences between treatments (nominal P < 0.01). The most common treatment-emergent adverse event with ripretinib was alopecia; however, QoL was similarly maintained out to treatment cycle 10, day 1 in patients receiving ripretinib who developed alopecia and those who did not.

CONCLUSION

PRO assessments in the INVICTUS trial suggest that patients on ripretinib maintain their QoL out to C2D1, unlike patients receiving placebo. Longitudinal QoL was maintained for patients receiving ripretinib out to cycle 10, day 1 (approximately 8 months; past the point of median progression-free survival with ripretinib [6.3 months]), even if the patients developed alopecia.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03353753 ; first posted: November 27, 2017.

Targeting Gatekeeper Mutations for Kinase Drug Discovery

Clinically acquired resistance is a major challenge in cancer therapies with small-molecule kinase inhibitors (SMKIs). Gatekeeper mutations in the ATP-binding pocket of kinases are the most common mutations leading to acquired resistance. To date, seven new-generation kinase inhibitors targeting gatekeeper mutations have been approved by the FDA; however, the clinical need is still unmet. Here, we systematically summarize the types of gatekeeper mutations across the kinase family, the structural basis for acquired resistance, and newly developed SMKIs targeting gatekeeper mutations as well as highlight the opportunities and challenges of kinase drug discovery for targeting gatekeeper mutations.

TIE2-high cervical cancer cells promote tumor angiogenesis by upregulating TIE2 and VEGFR2 in endothelial cells

Tyrosine kinase with immunoglobulin and epidermal growth factor homology domains 2 (TIE2), the receptor for angiopoietins, has been found highly expressed in cervical cancer and associated with poor prognosis. However, the potential role of tumoral TIE2 in cervical cancer angiogenesis and the underlying mechanisms remain unexplored. Here, based on multicolor immunofluorescence of 64 cervical cancer tissues, we found that TIE2 level in cervical cancer cells was positively related to shorter survival and higher microvessel density in tumor. In vitro and in vivo experiments verified that TIE2-high cervical cancer cells could promote tumor angiogenesis. TIE2-high tumor cells induced an amplified expression of TIE2 and vascular endothelial growth factor receptor 2(VEGFR2) in HUVECs to promote angiogenesis via TIE2 -AKT/MAPK signals, which could be reversed or partially reversed by TIE2, AKT or MAPK inhibitors and activated by angiopoietin-1 and angiopoietin-2. In conclusion, TIE2-high cervical cancer cells promote tumor angiogenesis by upregulating TIE2 and VEGFR2 in endothelial cells via TIE2-AKT/MAPK axis inside tumor cells.

Ripretinib Versus Sunitinib in Patients With Advanced Gastrointestinal Stromal Tumor After Treatment With Imatinib (INTRIGUE): A Randomized, Open-Label, Phase III Trial

PURPOSE

Sunitinib, a multitargeted tyrosine kinase inhibitor (TKI), is approved for advanced gastrointestinal stromal tumor (GIST) after imatinib failure. Ripretinib is a switch-control TKI approved for advanced GIST after prior treatment with three or more TKIs, including imatinib. We compared efficacy and safety of ripretinib versus sunitinib in patients with advanced GIST who were previously treated with imatinib (INTRIGUE, ClinicalTrials.gov identifier: NCT03673501).

PATIENTS AND METHODS

Random assignment was 1:1 to once-daily ripretinib 150 mg or once-daily sunitinib 50 mg (4 weeks on/2 weeks off) and stratified by KIT/platelet-derived growth factor α mutation and imatinib intolerance. The primary end point was progression-free survival (PFS) by independent radiologic review using modified Response Evaluation Criteria in Solid Tumors version 1.1. Secondary end points included objective response rate by independent radiologic review, safety, and patient-reported outcome measures.

RESULTS

Overall, 453 patients were randomly assigned to ripretinib (intention-to-treat [ITT], n = 226; KIT exon 11 ITT, n = 163) or sunitinib (ITT, n = 227; KIT exon 11 ITT, n = 164). Median PFS for ripretinib and sunitinib (KIT exon 11 ITT) was 8.3 and 7.0 months, respectively (hazard ratio, 0.88; 95% CI, 0.66 to 1.16; P = .36); median PFS (ITT) was 8.0 and 8.3 months, respectively (hazard ratio, 1.05; 95% CI, 0.82 to 1.33; nominal P = .72). Neither was statistically significant. Objective response rate was higher for ripretinib versus sunitinib in the KIT exon 11 ITT population (23.9% v 14.6%, nominal P = .03). Ripretinib was associated with a more favorable safety profile, fewer grade 3/4 treatment-emergent adverse events (41.3% v 65.6%, nominal P < .0001), and better scores on patient-reported outcome measures of tolerability.

CONCLUSION

Ripretinib was not superior to sunitinib in terms of PFS. However, meaningful clinical activity, fewer grade 3/4 treatment-emergent adverse events, and improved tolerability were observed with ripretinib.

A systematic review and network meta-analysis of the efficacy and safety of third-line and over third-line therapy after imatinib and TKI resistance in advanced gastrointestinal stromal tumor

Tyrosine kinase inhibitors (TKIs) have greatly improved the prognosis of unresectable and metastatic gastrointestinal stromal tumors (GISTs) in the last two decades. Imatinib and sunitinib are recommended as first-line and second-line therapies, respectively. However, there is a lack of precision therapy for refractory GISTs regarding therapy after imatinib and sunitinib. We comprehensively searched electronic databases, including PubMed, EMBASE, Web of Science, Cochrane Library, and ClinicalTrials, from inception to October 2022. Randomized controlled trials featuring comparisons with third-line or over third-line therapies against GISTs were eligible. The primary outcome was progression-free survival (PFS). All network calculations were performed using random effect models, and the ranking of regimens were numerically based on the surface under the cumulative ranking (SUCRA) statistics. A total of seven studies were eligible for inclusion in this network meta-analysis. After analysis, ripretinib was ranked at the top in progression-free survival (PFS), overall survival (OS), and disease control rate (DCR) (SUCRA statistics: 83.1%, 82.5%, and 86.5%, respectively), whereas nilotinib and pimitespib presented better tolerability (SUCRA statistics: 64.9% and 63.8%, respectively). We found that regorafenib seemed more reliable for clinical administration, and ripretinib showed good effectiveness for the over third-line therapy. Precise targeted therapy is a critical direction for the future treatment of GIST, and more high-quality studies of new agents are expected.

NCCN Guidelines® Insights: Gastrointestinal Stromal Tumors, Version 2.2022

Gastrointestinal stromal tumors (GIST) are the most common type of soft tissue sarcoma that occur throughout the gastrointestinal tract. Most of these tumors are caused by oncogenic activating mutations in the KIT or PDGFRA genes. The NCCN Guidelines for GIST provide recommendations for the diagnosis, evaluation, treatment, and follow-up of patients with these tumors. These NCCN Guidelines Insights summarize the panel discussion behind recent important updates to the guidelines, including revised systemic therapy options for unresectable, progressive, or metastatic GIST based on mutational status, and updated recommendations for the management of GIST that develop resistance to specific tyrosine kinase inhibitors.