FGFR inhibition augments anti-PD-1 efficacy in murine FGFR3-mutant bladder cancer by abrogating immunosuppression

The combination of targeted therapy with immune checkpoint inhibition (ICI) is an area of intense interest. We studied the interaction of fibroblast growth factor receptor (FGFR) inhibition with ICI in urothelial carcinoma (UC) of the bladder, in which FGFR3 is altered in 50% of cases. Using an FGFR3-driven, Trp53-mutant genetically engineered murine model (UPFL), we demonstrate that UPFL tumors recapitulate the histology and molecular subtype of their FGFR3-altered human counterparts. Additionally, UPFL1 allografts exhibit hyperprogression to ICI associated with an expansion of T regulatory cells (Tregs). Erdafitinib blocked Treg proliferation in vitro, while in vivo ICI-induced Treg expansion was fully abrogated by FGFR inhibition. Combined erdafitinib and ICI resulted in high therapeutic efficacy. In aggregate, our work establishes that, in mice, co-alteration of FGFR3 and Trp53 results in high-grade, non-muscle-invasive UC and presents a previously underappreciated role for FGFR inhibition in blocking ICI-induced Treg expansion.

Abstract 4867: Effect of FGFR3 activity on Nectin-4 expression in urothelial carcinoma

Bladder cancer is a common malignancy in the U.S. and cause of significant morbidity and mortality. Combination platinum-based chemotherapy has long been the mainstay in the treatment of metastatic urothelial carcinoma (mUC); however, over the last decade there have been significant advances in systemic therapy, which includes the FDA approval of the pan-FGFR inhibitor erdafitinib (approved for tumors with FGFR2/3 alterations) and the antibody drug conjugate (ADC) enfortumab vedotin (which targets the cell surface protein Nectin-4). Despite these advances, most patients with mUC will progress and succumb from their disease, highlighting the need for further therapeutic development. In parallel to therapeutic advances, there have been significant advances in the molecular characterization of UC, including identification of luminal and basal subsets. NECTIN4 and FGFR3 alterations are known to be enriched in luminal subtypes and we have found, via query of the TCGA data, that NECTIN4 expression was significantly higher in FGFR3 altered tumors. Given this association we sought to investigate the effect of FGFR3 activity on Nectin-4 expression. Using erdafitinib, in select luminal UC cell lines (RT112, RT4, SW780) with FGFR3 fusion proteins, we found, much to our surprise, that FGFR inhibition increased Nectin-4 expression. Western blots, probing for Nectin-4, following 24H, 48H, and 72H of treatment with erdafitinib (50 nM) showed a significant increase in protein expression in all three cell lines. Importantly, we consistently saw increased expression of what we believe corresponds to the membrane bound form of Nectin-4 and have now confirm such by flow cytometry and immunofluorescence probing for Nectin-4 in the RT112 cell line. We have also seen statistically significant increases in NECTIN4 on RT-PCR following treatment with erdafitinib; however, we believe that Nectin-4 regulation by FGFR inhibition is not merely transcriptional because the induction of Nectin-4 protein appears significantly greater than the fold increase in mRNA. Notably, in two additional UC cell lines (HT1376 - a luminal cell line with high Nectin-4 expression & UMUC3 - a basal cell line with low Nectin-4 expression), with no alterations in FGFR3, we did not see a significant change in Nectin-4 expression following treatment with erdafitinib. Based on our above results, we hypothesize that FGFR3 inhibition, in tumors harboring FGFR3 alterations, may act as a sensitize agent to Nectin-4 ADC targeted therapy; however, our results are preliminary and further investigation, particularly with in vivo models, is warranted.

Citation Format: Sean Clark-Garvey, Mi Zhou, Andrew Truong, Wolfgang Beckabir, Michael Sturdivant, William Kim. Effect of FGFR3 activity on Nectin-4 expression in urothelial carcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4867.

Brief Report: Improving Fellow Performance of the Pharmacology Section of the American Society of Clinical Oncology In-Training Exam

Though the electronic medical record has streamlined the process for ordering chemotherapy and reduced medical error, it has come at the cost of potentially hindering medical oncology fellows' acquisition of basic principles of chemotherapy administration. Recognizing the need for improving fellow knowledge and comfort level in chemotherapy prescription, we created an anticancer therapeutics curriculum for fellows at the University of North Carolina (UNC). The curriculum, which was comprised of a self-assessment, review session, and chemotherapy writing workshop, was offered voluntarily to all UNC fellows planning to take the medical oncology boards. We distributed a pre-intervention and post-intervention survey. In total, 11 of 18 fellows participated. After our interventions, there were statistically significant improvements in comfortability with calculating a dose of chemotherapy (p = 0.002), writing orders (p = 0.004), and taking the American Society of Clinical Oncology (ASCO) In-Training Exam (ITE) (p = 0.002). Furthermore, we saw a 4% overall improvement in pharmacology subset scores on the ITE compared to the prior year. Overall, our study suggested that the addition of a chemotherapy competency curriculum led to improved outcomes on the ASCO ITE, improved comfortability in chemotherapy administration, and hopefully improved patient care.

How to Conduct Clinical Trials of Personalized Cancer Therapies

We identified three important principles to guide clinical trials of personalized cancer therapies: (1) incorporation of developments in molecular cancer biology in trial design; (2) inclusion of biomarkers to guide rational therapy; (3) use of innovative trial designs.

RAF1 amplification: an exemplar of MAPK pathway activation in urothelial carcinoma

Despite recent therapeutic gains in the treatment of advanced bladder cancer, the overall survival in patients with metastatic disease remains poor and further therapeutic discovery is needed. Advanced bladder cancer is a molecularly heterogeneous disease, and the identification of driver genetic alterations has led to effective targeted therapeutic agents, such as fibroblast growth factor receptor (FGFR) inhibitors. In this issue of the JCI, Bekele et al. identify a subtype of muscle-invasive bladder cancer (MIBC) that harbors RAF1 amplification. The authors showed that RAF1 inhibition, with pan-RAF inhibitors, and the combination of RAF1 inhibition with MEK inhibition were efficacious in preclinical models harboring RAF1 amplifications as well as in tumors with HRAS and NRAS mutations. This study highlights RAF1 amplification as a driver event in bladder cancer and establishes the central role of the MAPK pathway in bladder tumorigenesis.

Targeting the Bcl-2 Family in B Cell Lymphoma

Although lymphoma is a very heterogeneous group of biologically complex malignancies, tumor cells across all B cell lymphoma subtypes share a set of underlying traits that promote the development and sustain malignant B cells. One of these traits, the ability to evade apoptosis, is essential for lymphoma development. Alterations in the Bcl-2 family of proteins, the key regulators of apoptosis, is a hallmark of B cell lymphoma. Significant efforts have been made over the last 30 years to advance knowledge of the biology, molecular mechanisms, and therapeutic potential of targeting Bcl-2 family members. In this review, we will highlight the complexities of the Bcl-2 family, including our recent discovery of overexpression of the anti-apoptotic Bcl-2 family member Bcl-w in lymphomas, and describe recent advances in the field that include the development of inhibitors of anti-apoptotic Bcl-2 family members for the treatment of B cell lymphomas and their performance in clinical trials.

A phase I dose-escalation trial of ublituximab (TG-1101), a novel anti-CD20 monoclonal antibody (mAb), for rituximab relapsed/refractory B-cell lymphoma patients

8575

Background: Anti-CD20 therapy (rituximab or RTX) in treating patients (pts) with B-cell lymphomas has resulted in significant improvement in treatment response and clinical outcomes. Despite advances, pts continue to relapse from, or are refractory to, RTX-based regimens. Ublituximab (UTX) is a novel, chimeric mAb targeting a unique epitope on the CD20 antigen. UTX has been glycoengineered to enhance affinity for all variants of FcγRIIIa receptors, and therefore demonstrates greater ADCC activity than RTX (Le Garff-Tavernier, 2011). UTX displayed greater antitumor activity compared to RTX in NHL in vivo models and in low CD20 expressing tumors (ASH 2011). A phase I trial with UTX used as a single agent in pts with relapsed/refractory CLL reported a response rate of 45%. Herein we report on the phase I dose-escalation of UTX in pts with RTX relapsed/refractory B-cell lymphoma. Methods: Eligible pts have B-cell lymphoma relapsed or refractory to a RTX containing regimen. Pts are required to have measurable/evaluable disease, ECOG PS < 2 and no active hepatitis B/C. The phase I dose-escalation uses a sequential 3+3 design in dose cohorts of 450mg, 600mg and 900mg respectively. UTX is administered once weekly for 4 infusions followed by monthly maintenance therapy. PK and correlative PD data are being collected. Primary endpoint: Maximum Tolerated Dose (MTD) and Dose Limiting Toxicities (DLT). Efficacy is a secondary endpoint. Results: Nine pts (5 FL, 3 MZL, 1 MCL) have been enrolled (3 each cohort). Median age 63; 3/6 (M/F). Median prior Rx = 4 (2-6). RTX refractory (44%). 8/9 pts are evaluable for safety; no DLT’s observed and no Grade 3/4 AE’s to date. 7/9 pts have had at least one response assessment (8 wk scan), which includes: 1 CR (rituximab refractory MZL); 2 PR’s (1 MZL, 1 FL); 2 SD (FL) and 2 PD (1 transformed FL, 1 MCL). PK analysis is ongoing. Conclusions: UTX has been well tolerated to date with no G 3/4 AE’s with demonstrated early clinical activity at all doses. 7/9 patients continue to receive UTX treatment (range 1–25 wks). Enrollment in the 900mg expansion cohort is now open with an emphasis on RTX relapsed/refractory indolent or low CD20-expressing lymphomas. Clinical trial information: NCT01647971.

Use of adjuvant 5-fluorouracil and radiation therapy after gastric cancer resection among the elderly and impact on survival

PURPOSE

In randomized trials patients with resected nonmetastatic gastric cancer who received adjuvant chemotherapy and radiotherapy (chemoRT) had better survival than those who did not. We investigated the effectiveness of adjuvant chemoRT after gastric cancer resection in an elderly general population and its effects by stage.

METHODS AND MATERIALS

We identified individuals in the Surveillance, Epidemiology, and End Results-Medicare database aged 65 years or older with Stage IB through Stage IV (M0) gastric cancer, from 1991 to 2002, who underwent gastric resection, using multivariate modeling to analyze predictors of chemoRT use and survival.

RESULTS

Among 1,993 patients who received combined chemoRT or no adjuvant therapy after resection, having a later year of diagnosis, having a more advanced stage, being younger, being white, being married, and having fewer comorbidities were associated with combined treatment. Among 1,476 patients aged less than 85 years who survived more than 4 months, the 313 who received combined treatment had a lower mortality rate (hazard ratio, 0.83; 95% confidence interval, 0.71-0.98) than the 1,163 who received surgery alone. Adjuvant therapy significantly reduced the mortality rate for Stages III and IV (M0), trended toward improved survival for Stage II, and showed no benefit for Stage IB. We observed trends toward improved survival in all age categories except 80 to 85 years.

CONCLUSIONS

The association of combined adjuvant chemoRT with improved survival in an overall analysis of Stage IB through Stage IV (M0) resected gastric cancer is consistent with clinical trial results and suggests that, in an elderly population, adjuvant chemoradiotherapy is effective. However, our observational data suggest that adjuvant treatment may not be effective for Stage IB cancer, is possibly appropriate for Stage II, and shows significant survival benefits for Stages III and IV (M0) for those aged less than 80 years.

Phase II trial evaluating the clinical and biologic effects of bevacizumab in unresectable hepatocellular carcinoma

PURPOSE

To determine the clinical and biologic effects of bevacizumab, an anti-vascular endothelial growth factor (VEGF) monoclonal antibody, in unresectable hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Adults with organ-confined HCC, Eastern Cooperative Oncology Group performance status of 0 to 2, and compensated liver disease were eligible. Patients received bevacizumab 5 mg/kg (n = 12) or 10 mg/kg (n = 34) every 2 weeks until disease progression or treatment-limiting toxicity. The primary objective was to determine whether bevacizumab improved the 6-month progression-free survival (PFS) rate from 40% to 60%. Secondary end points included determining the effects of bevacizumab on arterial enhancement and on plasma cytokine levels and the capacity of patients' plasma to support angiogenesis via an in vitro assay.

RESULTS

The study included 46 patients, of whom six had objective responses (13%; 95% CI, 3% to 23%), and 65% were progression free at 6 months. Median PFS time was 6.9 months (95% CI, 6.5 to 9.1 months); overall survival rate was 53% at 1 year, 28% at 2 years, and 23% at 3 years. Grade 3 to 4 adverse events included hypertension (15%) and thrombosis (6%, including 4% with arterial thrombosis). Grade 3 or higher hemorrhage occurred in 11% of patients, including one fatal variceal bleed. Bevacizumab was associated with significant reductions in tumor enhancement by dynamic contrast-enhanced magnetic resonance imaging and reductions in circulating VEGF-A and stromal-derived factor-1 levels. Functional angiogenic activity was associated with VEGF-A levels in patient plasma.

CONCLUSION

We observed significant clinical and biologic activity for bevacizumab in nonmetastatic HCC and achieved the primary study end point. Serious bleeding complications occurred in 11% of patients. Further evaluation is warranted in carefully selected patients.

Phase II trial evaluating the clinical and biologic effects of bevacizumab in unresectable hepatocellular carcinoma

PURPOSE

To determine the clinical and biologic effects of bevacizumab, an anti-vascular endothelial growth factor (VEGF) monoclonal antibody, in unresectable hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Adults with organ-confined HCC, Eastern Cooperative Oncology Group performance status of 0 to 2, and compensated liver disease were eligible. Patients received bevacizumab 5 mg/kg (n = 12) or 10 mg/kg (n = 34) every 2 weeks until disease progression or treatment-limiting toxicity. The primary objective was to determine whether bevacizumab improved the 6-month progression-free survival (PFS) rate from 40% to 60%. Secondary end points included determining the effects of bevacizumab on arterial enhancement and on plasma cytokine levels and the capacity of patients' plasma to support angiogenesis via an in vitro assay.

RESULTS

The study included 46 patients, of whom six had objective responses (13%; 95% CI, 3% to 23%), and 65% were progression free at 6 months. Median PFS time was 6.9 months (95% CI, 6.5 to 9.1 months); overall survival rate was 53% at 1 year, 28% at 2 years, and 23% at 3 years. Grade 3 to 4 adverse events included hypertension (15%) and thrombosis (6%, including 4% with arterial thrombosis). Grade 3 or higher hemorrhage occurred in 11% of patients, including one fatal variceal bleed. Bevacizumab was associated with significant reductions in tumor enhancement by dynamic contrast-enhanced magnetic resonance imaging and reductions in circulating VEGF-A and stromal-derived factor-1 levels. Functional angiogenic activity was associated with VEGF-A levels in patient plasma.

CONCLUSION

We observed significant clinical and biologic activity for bevacizumab in nonmetastatic HCC and achieved the primary study end point. Serious bleeding complications occurred in 11% of patients. Further evaluation is warranted in carefully selected patients.