Optimal dose of sunitinib for long-term treatment in Japanese patients with renal cell carcinoma

PDZK1 confers sensitivity to sunitinib in clear cell renal cell carcinoma by suppressing the PDGFR-β pathway

BACKGROUND

Sunitinib has emerged as the primary treatment for advanced or metastatic clear cell renal cell carcinoma (ccRCC) due to its significant improvement in patients' average survival time. However, drug resistance and adverse effects of sunitinib pose challenges to its clinical benefits.

METHODS

The differentially expressed genes (DEGs) associated with sunitinib sensitivity and resistance in ccRCC were investigated. Cell counting kit-8, plate colony formation, flow cytometry and subcutaneous xenograft tumor model assays were employed to explore the effects of PDZK1 on ccRCC. Further research on the molecular mechanism was conducted through western blot, co-immunoprecipitation, immunofluorescence co-localization and immunohistochemical staining.

RESULTS

We elucidated that PDZK1 is significantly downregulated in sunitinib-resistant ccRCC specimens, and PDZK1 negatively regulates the phosphorylation of PDGFR-β and the activation of its downstream pathways through interaction with PDGFR-β. The dysregulated low levels of PDZK1 contribute to inadequate inhibition of cell proliferation, tumor growth, and insensitivity to sunitinib treatment. Notably, our preclinical investigations showed that miR-15b antagomirs enhance sunitinib cytotoxic effects against ccRCC cells by upregulating PDZK1 levels, suggesting their potential in overcoming sunitinib resistance.

CONCLUSIONS

Our findings establish the miR-15b/PDZK1/PDGFR-β axis as a promising therapeutic target and a novel predictor for ccRCC patients' response to sunitinib treatment.

Sunitinib therapy for imatinib-resistant and/or intolerant gastrointestinal stromal tumors: comparison of safety and efficacy between standard and reduced dosage regimens

BACKGROUND

Sunitinib therapy for patients with imatinib-resistant and/or intolerant gastrointestinal stromal tumors (GISTs) often causes severe adverse events (AEs) that lead to treatment discontinuation.

METHODS

We retrospectively reviewed the clinical records of imatinib-resistant and/or intolerant GIST patients who underwent sunitinib therapy in our institutions between 2007 and 2020. Forty-one patients were enrolled and divided into two groups on the basis of the starting dosage: the standard dosage group (50 mg/day, 21 patients) and the reduced dosage group (37.5 mg/day, 20 patients). Tolerability, safety and clinical efficacy of the two groups were compared.

RESULTS

Three patients (14%) in the standard dosage group and another three (15%) in the reduced dosage group (P = 1.000) discontinued sunitinib therapy because of AEs. The incidences of grade 3 or more severe treatment-related AEs were 90 and 75%, respectively (P = 0.238). Two possible treatment-related deaths were noted in the standard dosage group. Clinical efficacy was comparable between the two groups: median time to treatment failure and overall survival were 4.5 months [interquartile range (IQR), 3.6-9.0] and 13.7 months (IQR, 7.5-22.9) in the standard dosage group and 4.6 months (IQR, 2.7-17.0) and 13.4 months (IQR, 9.3-36.8) in the reduced dosage group, respectively.

CONCLUSIONS

The reduced dosage of 37.5 mg sunitinib tended to decrease toxicity and the incidences of severe AEs and treatment-related deaths. This reduced dosage regimen showed equivalent clinical efficacy including patient survival. The reduced dosage of 37.5 mg sunitinib can be adopted as an alternative therapy for patients with imatinib-resistant and/or intolerant GISTs.

Cabozantinib in advanced renal cell carcinoma: A phase II, open-label, single-arm study of Japanese patients

Objectives

To evaluate the efficacy and safety of cabozantinib, through a bridging study to METEOR, in Japanese patients with advanced renal cell carcinoma who had progressed after prior tyrosine kinase inhibitor therapy.

Methods

This phase II, open‐label, single‐arm study (ClinicalTrials.gov registration number: NCT03339219) included adult Japanese patients with advanced renal cell carcinoma and measurable disease who had received one or more tyrosine kinase inhibitors. Patients received cabozantinib 60 mg orally once daily while there was clinical benefit, or until unacceptable toxicity or disease progression. The primary end‐point was objective response rate per Response Evaluation Criteria in Solid Tumors Version 1.1. Secondary end‐points included clinical benefit rate (complete or partial response, or ≥8‐week stable disease), progression‐free survival, overall survival and safety.

Results

Of the 35 patients enrolled, 68.6%, 22.9% and 8.6% had previously received one, two and three prior tyrosine kinase inhibitors, respectively. The median duration of cabozantinib exposure was 27.0 weeks (range 5.1–43.0 weeks). The objective response rate was 20.0% (90% confidence interval 9.8–34.3%), and the clinical benefit rate was 85.7% (95% confidence interval 69.7–95.2%). The 6‐month estimated progression‐free survival was 72.3% (95% confidence interval 53.3–84.6%); the median progression‐free survival and overall survival were not reached. All patients reported adverse events, which were manageable by supportive treatment or dose modification; two patients (5.7%) discontinued therapy due to adverse events.

Conclusions

The results showed that findings from METEOR can be extrapolated, and that cabozantinib 60 mg/day is a viable treatment option in Japanese patients with advanced renal cell carcinoma who had progressed after prior tyrosine kinase inhibitor therapy.