Krithika  Subramanian , PhD

In 2020, the role of immune checkpoint inhibitors (ICIs) in urothelial cancer expanded beyond second-line treatment of patients with locally advanced/ metastatic disease. Based on data from the phase 3 JAVELIN Bladder 100 trial (NCT02603432), the FDA granted approval to the PD-L1 inhibitor avelumab (Bavencio) as maintenance therapy for patients with locally advanced or metastatic urothelial cancer who did not progress on first-line platinum chemotherapy.

“Avelumab first-line maintenance in patients whose disease has not progressed with platinum-based induction chemotherapy represents a new standard first-line treatment for advanced urothelial cancer,” Thomas Powles, MD, MBBS, said during a presentation at the 2020 American Society of Clinical Oncology Virtual Scientific Program.

After decades of dormancy, the therapeutic landscape of locally advanced/metastatic urothelial cancer underwent a paradigm shift—with multiple regulatory approvals of ICIs as second-line treatment—leading to changes in guideline-recommended management of patients in this setting.

Per the National Comprehensive Cancer Network guidelines, pembrolizumab (Keytruda), atezolizumab (Tecentriq), nivolumab (Opdivo), durvalumab (Imfinzi), and avelumab are suitable systemic therapy options for patients who already received or who are ineligible for platinum-based chemotherapy based on durable responses and acceptable toxicity profiles.

However, outcomes in patients with disease that relapses following platinum-based chemotherapy, the mainstay of frontline therapy, are poor. Disease progression within approximately 9 months of treatment occurs in most patients treated with a combination platinum-based chemotherapy regimen.4 Therefore, therapies that improve outcomes in locally advanced/metastatic urothelial carcinoma, including in patients who have already received platinum, continue to be an area of clinical focus. 

“Although most patient s with advanced [urothelial carcinoma] have disease control or indeed a response to first-line platinum-based chemotherapy, progression-free survival and overall survival are short, and this is because resistance to this disease occurs quickly,” said Powles, a professor of genitourinary oncology, group lead for Solid Tumour Research, and director of the Barts Cancer Center in London, United Kingdom.4 “After first-line chemotherapy, only a minority of patients get second-line treatment.”

JAVELIN Bladder 100 Data The JAVELIN Bladder 100 trial evaluated the potential for ICI therapy with avelumab as maintenance in patients with unresectable locally advanced or metastatic urothelial carcinoma who did not have disease progression on first-line chemotherapy. 

The investigators’ rationale for introducing maintenance immunotherapy in this setting was the result of prolonged survival data observed in other solid tumors. In addition, urothelial carcinomas express high levels of PD-L1, harbor DNA repair mutations, and have a high tumor mutational burden, all of which have been associated with response to ICI therapy in other tumor types.

Similarly, data have shown that initial chemotherapy can enhance the effects of subsequent ICI therapy via immune priming and depletion of immunosuppression

 and that chemotherapy and ICIs are not cross-resistant, providing an earlier avenue for use of this clinically active treatment in urothelial carcinoma.

In total, 700 patients were randomized 1:1 to receive best supportive care with or without maintenance avelumab. The primary end point was overall survival (OS), and progression-free survival (PFS) and safety were secondary end points. Baseline characteristics of the avelumab and the best supportive care arms were well balanced in the overall population, with 55% of patients in both arms having visceral metastasis; 54% and 48%, respectively, having positive PD-L1 status; and 52% and 59% having received gemcitabine and cisplatin as first-line therapy. The majority of patients, at 72% in each arm, had either a partial or complete response to frontline chemotherapy.

The data showed that the addition of maintenance avelumab to best supportive care significantly prolonged OS compared with best supportive care alone, with medians of 21.4 months versus 14.3 months (HR, 0.69; 95% CI, 0.56-0.86; 

 < .001). The corresponding 1-year OS rates were 71.3% and 58.4%, respectively. Avelumab was also shown to prolong survival in the subset of patients with PD-L1–positive tumors, with a median OS that was not evaluable versus 17.1 months in the best supportive care arm (HR, 0.56; 95% CI, 0.40-0.79; 

 < .001). The 1-year OS rates were 79.1% and 60.4%, respectively.

The median PFS was also extended in the overall population, at 3.7 months versus 2.0 months for the experimental and control arms, respectively (HR, 0.62; 95% CI, 0.52-0.75; 

<.001). The PD-L1–positive cohort showed similar PFS benefit, with corresponding medians of 5.7 months and 2.1 months (HR, 0.56; 95% CI, 0.43-0.73; 

As expected, higher incidence of adverse events occurred with avelumab than in the control group, with grade 3 or higher events reported in 47.4% and 25.2% of patients, respectively. No new safety signals for avelumab were identified.

Following these data, updated analyses of the trial presented at the European Society for Medical Oncology Virtual Congress 2020 suggested that patients benefit from the addition of avelumab to best supportive care regardless of PD-L1 expression or other baseline characteristics, such as ECOG performance status or response to frontline chemotherapy. These results taken together led the investigators to conclude that avelumab may be used in patients as maintenance therapy, regardless of PD-L1 expression status, and that further investigations may be necessary to reveal prognostic tumor biomarkers.

Pembrolizumab as “Switch” Maintenance 

The PD-1 inhibitor pembrolizumab is another ICI that has been investigated as switch maintenance therapy following platinum combinations based on the same rationale that motivated the JAVELIN Bladder 100 trial. According to the GU14-182 trial [NCT02500121] authors, led by Matthew Galsky, MD, switch maintenance is defined as “the initiation of immune checkpoint blockade immediately after cessation of firstline platinum-based chemotherapy.”

“With regard to switch maintenance approaches…it’s important to step back and think about what we are trying to achieve in this setting,” Galsky, director of genitourinary medical oncology and professor of urology, medicine and medical oncology at The Tisch Cancer Institute at Icahn School of Medicine at Mount Sinai in New York, said in an interview with Targeted Therapies in Oncology. “One of the potential benefits of immune checkpoint blockade as a switch maintenance strategy as opposed to other things that have been explored in this setting, [including] non–cross-resistant chemotherapies, is that you are hoping to allow patients to have their responses maintained or improved but at the same time give them a break from the toxicity of chemotherapy. The more we add in terms of adverse effect burden in that setting, [the more] we start to diminish what we are trying to achieve.”

In the double-blind phase 2 trial, 108 patients with metastatic urothelial carcinoma achieving at least stable disease on first-line cisplatin- or carboplatin-based combination chemotherapy regimens were randomized 1:1 to intravenous pembrolizumab at 200 mg once every 3 weeks (n=55) as switch maintenance versus placebo (n=53) for up to 24 months. Patients with disease progression could cross over to pembrolizumab. The primary end point was PFS, with OS and treatment outcomes per PD-L1 combined positive score as the secondary end points.

The median PFS was significantly longer with maintenance pembrolizumab versus placebo, at 5.4 months versus 3.0 months, respectively (HR, 0.65; log-rank 

=.04). Pembrolizumab maintenance yielded an objective response rate of 23% compared with 10% in the placebo group. The median OS with pembrolizumab was 22.0 months versus 18.7 months with placebo (HR, 0.91; 95% CI, 0.52-1.59). Interestingly, PD-L1 expression levels did not seem to have an impact on PFS or OS between arms. 

“Theoretical advantages to a sequential, compared with a concurrent, combination approach, include the lack of concomitant administration of immune suppressive chemotherapy and corticosteroid antiemetic prophylaxis,” wrote Galsky and colleagues. “Ultimately, the outcomes of the several pending randomized trials will together shape the near-term landscape of first-line treatment of metastatic urothelial cancer, a disease state characterized by a paucity of advances in decades.”

Galsky and colleagues noted that data for ongoing trials, including the IMvigor130 trial [NCT02807636] comparing atezolizumab as monotherapy or in combination with platinum-based chemotherapy versus placebo in previously untreated locally advanced or metastatic urothelial carcinoma may help clarify the utility of advancing ICI therapy earlier in the treatment line.

With the approval of avelumab maintenance therapy, the role and timing of immune checkpoint blockade in metastatic urothelial carcinoma treatment continue to be refined. Data from trials investigating pembrolizumab switch, or sequential, maintenance and atezolizumab as first-line monotherapy or concurrent with platinum chemotherapy will likely further clarify the optimal sequencing of monotherapy and combination regimens of ICIs in locally advanced or metastatic disease. Positive data from these trials could likely result in opportunities for their use as first-line treatments and in patients who may be ineligible for, refuse, or are unable to tolerate platinum regimens. 

1. FDA approves avelumab for urothelial carcinoma maintenance treatment. FDA. Updated July 1, 2020. Accessed November 4, 2020. https:// bit.ly/2IwgpfN 

2. Powles P, Park SH, Voog E, et al. Maintenance avelumab + best supportive care (BSC) versus BSC alone after platinum-based first-line (1L) chemotherapy in advanced urothelial carcinoma (UC): JAVELIN Bladder 100 phase III interim analysis. J

. 2020;38(suppl 18):LBA1. doi:10.1200/JCO.2020.38.18_suppl.LBA1 

3. NCCN. Clinical Practice Guidelines in Oncology. Bladder cancer, version 6.2020. Accessed November 12, 2020. https://bit.ly/2IxHHlC 

4. Powles T, Park SH, Voog E, et al. Avelumab maintenance therapy for advanced or metastatic urothelial carcinoma. 

. 2020;383(13):1218-1230. doi:10.1056/NEJMoa2002788 

5. Hato SV, Khong A, de Vries IJM, Lesterhuis WJ. Molecular pathways: the immunogenic effects of platinum-based chemotherapeutics. 

. 2014;20(11):2831-2837. doi:10.1158/1078-0432.CCR-13-3141 

6. Galsky MD, Chowdhury S, Bellmunt J, et al. Treatment patterns and outcomes in “real world” patients (pts) with metastatic urothelial cancer (UC). 

. 2020;31(suppl 15):4525. doi:10.1200/jco.2013.31.15_ suppl.4525

Articles

After decades of dormancy, the therapeutic landscape of locally advanced/metastatic urothelial cancer underwent a paradigm shift—with multiple regulatory approvals of immune checkpoint inhibitors as second-line treatment—leading to changes in guideline-recommended management of patients in this setting.

Frontline Maintenance Therapy for Urothelial Cancer Emerges

Identification of key oncogenic drivers and the development of targeted therapies with clinical activity in patients harboring actionable mutations have revolutionized the treatment paradigm in non–small cell lung cancer (NSCLC), redirecting attention toward advances in biomarker testing methodologies. This new focus is poised to foster granular refinement of precise, targeted treatment of lung tumors.

Advances in NSCLC research have enabled an understanding of the disease as a collection of molecular subgroups. The proliferation of alteration-matched therapies specific to these subgroups is a prime example of a precision medicine approach. In addition to oncogenic driver mutations, therapeutic response biomarkers have been identified, such as PD-L1 expression as a predictor of immunotherapy efficacy.

Underscoring the importance of biomarker-guided treatment approaches, guidelines for molecular testing in NSCLC include an extensive list of alterations, such as sensitizing 

The list continues to expand beyond these established canonical markers, with the addition of variants such as 

 exon 14 skipping mutations and tumor mutational burden. In fact, the FDA recently approved therapies specific for tumors with these molecular characteristics.

The rapid pace of biomarker discovery, characterization of molecular subtypes of NSCLC, development of matched targeted therapies, and regulatory approval of companion diagnostic tests has accelerated progress in the delivery of optimal care for patients with advanced NSCLC. Areas where continued optimization is particularly emphasized include determining which type of sample(s) should be tested, which biomarkers should be analyzed in different patient subsets, and which assays are most appropriate for specific (sets of) markers, as well as logistical and administrative factors, such as turnaround times and cost/reimbursement considerations.

Key Considerations for Molecular Testing in Lung Tumors

As biomarker testing in NSCLC evolves, investigators continue to evaluate testing approaches with the goal of standardizing the process of oncogenic driver identification.

At the 2020 Molecular Analysis for Precision Oncology (MAP) Virtual Congress, held October 9 to 10, 2020, presentations focused on recent developments in molecular testing, including the results of studies comparing testing methods for aberrations in the 

Gain-of-function alterations in MET, which encodes a receptor tyrosine kinase, drive oncogenesis. One such alteration with important implications for NSCLC is MET exon 14 skipping, resulting from several types of mutation in either exon 14 itself, the adjacent introns, or the flanking splice sites. Regardless, the effect is the same: a critical ubiquitination site is lost, which leads to MET protein accumulation and activation, enhancing MET pathway signal transduction and culminating in tumorigenesis. Previously, immunohistochemistry was typically performed to detect 

overexpression due to copy number changes. However, next-generation sequencing (NGS) is now the preferred testing method because it can also identify 

 exon 14 skipping mutations, the primary driver of oncogenesis.

 exon 14 skipping mutations are actionable because the resultant protein is responsive to MET inhibition using tyrosine kinase inhibitors (TKIs) such as capmatinib (Tabrecta),

 which was approved in May 2020 for use in adult patients with metastatic NSCLC harboring a 

 Compared with their sensitivity to specific TKIs, this subset of patients has exhibited lower rates of response to immunotherapy despite frequent tumor expression of PD-L

 suggesting a dual predictive role for the 

 exon 14 skipping mutation as a biomarker.

In a study presented at MAP 2020, tumor samples from patients with NSCLC and no other driver mutations were tested for 

 exon 14 skipping mutations over a period of 14 months. The investigators compared 2 DNA-based methods: NGS on the Ion Proton platform using AmpliSeq technology and fragment analysis using polymerase chain reaction (PCR) and size-based electrophoretic separation of the amplicons for detection of large deletions.

Of the 87 patient samples tested, 13 were determined to have a 

 exon 14 skipping alteration, with 5 harboring splice variants and 8 carrying deletions affecting the splice site. Two of these deletions were large, spanning 41 and 66 base pairs; they were detected by fragment analysis but not NGS. Although NGS is widely considered superior to single-gene assays, these data indicate that it may have limitations in detecting specific alterations and that “complementary methods or large-coverage intron screening could be an alternative” for optimal detection of 

 alterations to inform selection of first-line treatment, according to lead study author Romain Loyaux, from the Molecular Oncology Department of Georges-Pompidou European Hospital–APHP in Paris, France.

Commenting on the failure of the NGS assay to detect large 

 exon 14 deletions, Loyaux stated that “fragment analysis is a cheap and robust method to detect large deletions, especially when no RNA is available” (FIGURE).9-11 He noted that anchored, multiplex, targeted RNA-based NGS, like the technology developed by the Archer company, may be a good alternative when RNA is available; however, it has a 20% failure rate.

 genes, which encode a family of receptor tyrosine kinases, result in a constitutively activated chimeric protein that promotes oncogenesis and therefore, can be therapeutically targeted with TKIs.

Two FDA-approved TKIs, entrectinib (Rozlytrek) and larotrectinib (Vitrakvi), have activity in 

Broad, hybrid-capture DNA-based NGS, with RNA-based anchored multiplex PCR as an adjunct, are currently the primary methods of detecting 

 gene fusions in patients with lung cancer.

 The availability of entrectinib and larotrectinib will likely foster further development of 

 fusion detection methods for use in routine clinical practice.

A recent study presented at MAP 2020 evaluated the analytical performance—namely, sensitivity, specificity, and precision—of 3 commonly available RNA-based NGS assays. The assays examined were TruSight Oncology 500 (TSO500) by Illumina, Oncomine Focus Assay (OFA) by Thermo Fisher Scientific, and Fusion- Plex Lung (AFL) by Archer.

The limits of sensitivity and precision were assessed using droplet digital PCR with admixtures of both 

 fusion–positive and –negative samples, whereas specificity was evaluated using 

 fusion–negative clinical samples. The data showed that all 3 NGS assays successfully detected 

 fusions; however, technical differences between the assays may impact their performance. For instance, although all tested assays demonstrated strong specificity, the sample metrics were variable. Quality control (QC) success rates for OFA and TSO500 were 83% and 77%, respectively, but only 43% of samples on AFL passed all assay QC metrics. Notably, the different assays missed specific 

Clinical Utility of NGS Panels of Different Sizes

It has been established that multigene panels are superior to single-gene assays for biomarker testing in NSCLC2; however, data to inform clinicians’ selection of specific NGS gene panels have been lacking.

In a recent study presented at MAP 2020, a literature review was conducted to compare 2 commercially available DNA-based NGS gene panels: the Ion AmpliSeq Cancer Hotspot Panel, covering hotspots in 50 genes (Panel 50); and the FoundationOne panel, covering the complete exons of 315 genes (Panel 315). The clinical utility of each panel was determined based on the number of detectable actionable alterations in various solid tumor types that it contained. The data showed a substantial gain in actionability using the larger gene panel, which matched more actionable genetic mutations to FDA-approved or experimental drugs; the number of actionable alterations in various solid tumor types using Panel 315 was a median 50% higher compared with Panel 50 (t test, 

 <.001). The authors attributed this gain to the inclusion of more genes related to homologous recombination repair deficiency and microsatellite instability/immunotherapy response in the larger panel.

In the current era of precision medicine in lung cancer, defined histological subtyping, oncogenic driver testing, and analysis of tumor PD-L1 expression/immunotherapy sensitivity are crucial steps prior to therapeutic decision-making in NSCLC. As additional targeted agents are investigated in clinical trials and the incidence of their molecular targets are characterized in patient populations, expanded molecular testing may become necessary.

Molecular pathologists will continue to play an integral role in the continuum of care in NSCLC, from diagnosis to clinical decision-making based on biomarker detection. Molecular testing is likely to expand rapidly, and additional molecular subtypes will be identified that help match more patients with the optimal targeted therapies, providing highly personalized treatment plans.

Details of analytical procedures and assays will continue to be refined.

 By combining defined sets of biomarkers with appropriate protocols for collecting NSCLC samples and optimized methods for assessing specific changes, clinicians will be able to actualize the promise of precision medicine for patients with this challenging malignancy.

1. Lindeman NI, Cagle PT, Aisner DL, et al. Updated molecular testing guideline for the selection of lung cancer patients for treatment with targeted tyrosine kinase inhibitors: guideline from the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology. 

. 2018;142(3):321-346. doi:10.5858/arpa.2017-0388-CP

2. NCCN. Clinical Practice Guidelines in Oncology. Non-small cell lung cancer, version 8.2020. Accessed October 26, 2020. https://bit.ly/2TKomAj

3. FDA grants accelerated approval to capmatinib for metastatic nonsmall cell lung cancer. FDA. May 6, 2020. Accessed November 2, 2020. https://bit.ly/360o7Xg

4. FDA approves pembrolizumab for adults and children with TMB-H solid tumors. FDA. June 16, 2020. Accessed November 2, 2020. https://bit.ly/2HWB64q

5. Smeltzer MP, Wynes MW, Lantuejoul S, et al. The International Association for the Study of Lung Cancer global survey on molecular testing in lung cancer. 

l. 2020;15(9):1434-1448. doi:10.1016/j.jtho.2020.05.002

6. Wempe MM, Stewart MD, Glass D, et al. A national assessment of diagnostic test use for patients with advanced NSCLC and factors influencing physician decision-making. 

7. Sabari JK, Santini F, Bergagnini I, Lai WV, Arbour KC, Drilon A. Changing the therapeutic landscape in non-small cell lung cancers: the evolution of comprehensive molecular profiling improves access to therapy. 

. 2017;19(4):24. doi:10.1007/s11912-017-0587-4

8. Sabari JK, Montecalvo J, Chen R, et al. PD-L1 expression and response to immunotherapy in patients with MET exon 14-altered non-small cell lung cancers (NSCLC).

. 2017;35(suppl 15):8512. doi:10.1200/JCO.2017.35.15_suppl.8512

9. Loyaux R, Blons H, Garinet S, Urban P, Leger C, Bastide M. MET exon 14 screening strategy: how not to miss large deletions. 

. 2020;31(suppl 5): S1217-S1239. doi:10.1016/j.annonc.2020.08.2163

10. Pruis MA, Geurts-Giele WRR, von der TJH, et al. Highly accurate DNAbased detection and treatment results of MET exon 14 skipping mutations in lung cancer. Lung Cancer. 2020;140:46-54. doi:10.1016/j.lungcan.2019.11.010

11. Davies KD, Lomboy A, Lawrence CA, et al. DNA-based versus RNAbased detection of MET exon 14 skipping events in lung cancer.

. 2019;14(4):737-741. doi:10.1016/j.jtho.2018.12.020

12. Cohen D, Hondelink LM, Solleveld-Westerink N, et al. Optimizing mutation and fusion detection in NSCLC by sequential DNA and RNA sequencing. 

. 2020;15(6):1000-1014. doi:10.1016/j.jtho.2020.01.019

13. FDA approves entrectinib for NTRK solid tumors and ROS-1 NSCLC. FDA. Published August 15, 2019. Accessed October 28, 2020. https://bit.ly/3mPhUEB

14. FDA approves larotrectinib for solid tumors with NTRK gene fusions. FDA. Published November 26, 2018. Accessed October 28, 2020. https://bit.ly/381dXZe

15. Bormann Chung C, Lee J, Barritault M, et al. Evaluating targeted next-generation sequencing (NGS) assays and reference materials for 

 fusion detection. Ann Oncol. 2020;31(suppl 5):S1221. doi:10.1016/j.annonc.2020.08.2172

16. Özdemir B, Charrier M, Gerard CL, et al. Comparison of the clinical utility of two different size next generation sequencing (NGS) gene panels for solid tumours. 

l. 2020;31(suppl 5):S1219. doi:10.1016/j.annonc.2020.08.2166

17. Pennell NA, Arcila ME, Gandara DR, West H. Biomarker testing for patients with advanced non-small cell lung cancer: real-world issues and tough choices. 

. 2019;39:531-542. doi:10.1200/EDBK_237863

Identification of key oncogenic drivers and the development of targeted therapies with clinical activity in patients harboring actionable mutations have revolutionized the treatment paradigm in non–small cell lung cancer, redirecting attention toward advances in biomarker testing methodologies.

Increased Attention on Testing for Oncogenic Drivers in NSCLC Advances the Promise of Precision Medicine

The clinical development and application of cancer immunotherapy over the past decade has translated the long-standing knowledge of the close relationship between cancerous tissues and lymphoid immune cells, dating back to the late 19th century.

Today, cancer immunotherapies, all of which recruit the body&rsquo;s own immune system to target and eliminate cancer cells, represent a rapidly expanding and paradigm-shifting arsenal in cancer treatment. Immunotherapies that have gained regulatory approval and/or are in clinical development include immune checkpoint blockade agents, chimeric antigen receptor (CAR) T-cell therapy, cancer vaccines, and adoptive or engineered T cellbased therapies

&ldquo;Living Drugs&rdquo;: An Overview of Adoptive T-Cell Therapies

In adoptive cell therapy (ACT), the intrinsic antitumor cytotoxic activity of the host immune system, especially antitumor cytotoxic T lymphocytes (CTLs), is harnessed to target and eliminate tumor cells by adoptive transfer of tumor-associated antigen-specific CTLs derived either from the tumor itself (tumor infiltrating lymphocytes [TILs]) or from peripheral blood (patient lymphocytes engineered to target tumor antigens in CAR T- or engineered T-cell receptor [TCR] cellular therapies). A remarkable feature of all types of ACT is the potential for personalization. All current ACT treatments use autologous T cells as the initial resource that is then customized to generate a &ldquo;living drug&rdquo; highly specific to the individual patient and their cancer. The fundamentals, current scope, and emerging concepts of ACT in cancer are the focus of a presentation by Patrick Hwu, MD, division head, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center during the Society for Immunotherapy of Cancer&rsquo;s 34th Annual Meeting (SITC 2019).

TIL Therapy: Modulating the TILTumor Microenvironment Interaction

Steven A. Rosenberg, MD, PhD, and colleagues lay the foundation for TIL therapy nearly 40 years ago when they demonstrated that lymphocytes extracted from freshly resected melanomas, expanded ex vivo, and infused back into the patients could induce high response rates in patients with metastatic melanoma.

Solid tumors are infiltrated by many immune cells, including T and B lymphocytes, natural killer cells, dendritic cells, and macrophages. Among these, TILs are thought to indicate an antitumor immune response and have been identified as favorable prognostic indicators in many cancers including melanoma and breast cancer.

TILs also affect treatment response; for instance, the relative abundance of CD8-positive (+) TILs predicted response to antiPD-1 therapy in melanoma and the presence of TILs, along with PD-L1 expression, correlated with pathologic complete response rates to neoadjuvant chemotherapy in breast cancer.

&ldquo;We started utilizing [TIL therapy] first in melanoma,&rdquo; said Hwu, who was previously at the National Cancer Institute working with the TIL pioneer Rosenberg on some of the earliest ACT studies, &ldquo;but we&rsquo;re now investigating [TIL immunotherapy] in a number of other cancer types, including pancreatic, ovarian, and colon cancers.&rdquo; Clinical data on TILs in metastatic melanoma have been consistently promising, and TILs have been produced successfully for other cancers.

Clinical data on TILs for metastatic melanoma have consistently been promising, and TILs have been successfully produced for other cancers.

The high mutation-al load and high neoantigen rates are thought to account for the significant and consistent clinical benefit of TIL therapy in patients with metastatic melanoma, whereas the heterogeneity in these key attributes, as well as key differences in the tumor microenvironment (TME), may account for the variability in tumor reactivity of TILs in other solid tumors. Hwu and colleagues are evaluating strategies to enhance the survival and activity of TILs in the context of the tumor microenvironment. In one such innovative approach, they have inserted the gene encoding a dominant-negative form of the transforming growth factor (TGF)-&beta; _receptor into immune cells.

Tumors, tumor-associated stromal cells, and regulatory T cells (Tregs) produce large quantities of TGF-&beta;, which acts as a key immunosuppressant in the TME.

Introduction of the decoy TGF-&beta; _receptor depletes TGF-&beta; _in the TME without invoking TGF-&beta; _immunosuppressive activity, which allows the TILs to mount a robust antitumor immune response. Speaking to the clinical utility of this approach, Hwu said, &ldquo;[Using this approach], we have obtained clinical responses in metastatic melanoma patients with disease resistant to the standard-of-care [therapy], including the immune checkpoint blockade agents, such as anti-PD-1 antibodies. Even if the patients had progressed after antiPD-1 therapy, this mode of [TIL] therapy has yielded durable responses in some patients thus far.&rdquo; He added that they use of the TGF-&beta; _decoy receptor may be a feasible approach in other ACTs.

CAR T-Cell Therapies Overcoming Resistance

CAR T-cellbased immunotherapy relies on the recognition of antigens expressed on the tumor cell surface by the synthetic CARs transduced into autologous T cells. CARs are synthetic receptors generally constructed by fusing an antigen-specific single-chain antibody fragment with signaling molecules of the TCR/CD3 complex, usually the CD3&zeta; _chain. Although CD19 is the most studied CAR target, the intracellular domain of the engineered CAR may also contain costimulatory modules that stimulate T cell activation, proliferation, and cytokine production

CAR-T cell therapy has yielded promising data in hematologic malignancies, especially B-cell neoplasms.

&ldquo;As the work on CD19-targeted CAR T-cell therapy has matured, it looks like some patients progress even after an initial response to the CAR T therapy,&rdquo; Hwu said, alluding to the significant clinical challenge of resistance to CAR T-cell therapy. He pointed to studies that have helped uncover the key mechanisms of development of resistance to CAR T-cell therapy, including loss of tumor antigen (eg, loss of tumor CD19 expression) and loss of T cell &ldquo;fitness&rdquo; over time.

Engineered TCR-Based Therapies: A Look Ahead

In TCR gene therapy, a novel TCR is introduced into patient-derived T cells by engrafting genes that encode TCR-&alpha; _and &beta; _chains to allow the cells to recognize tumor antigens in an MHC-dependent manner.

The potency of TCRs depends on their interaction with peptide- MHC complexes that are tumor-specific or are enriched in the tumor. Tumor-associated antigens can be encoded by mutated genes (neoantigens) or can be derived from proteins that are overexpressed in tumors. TCRs from T cells harboring HLA alleles matching the class in the antigen-presenting cells recognize peptide-major histocompatibility complex (pMHCs)and ultimately promote the killing of cancer cells. While most current TCR therapies use MHC class Irestricted TCRs to genetically modify CD8+ T cells or bulk T cells for patient treatment, recent evidence suggests that TCR-engineered MHC class II-restricted CD4+ T cells may also have utility in cancer immunotherapy. &ldquo;Many groups are now trying to develop a library of TCR genes to target various tumors, based on what tumor antigens and human leukocyte antigen (HLA) alleles are being expressed in individual patients, to allow for transduction of the HLA-matched TCRs for adoptive T-cell transfer,&rdquo; Hwu said. &ldquo;This approach has [already been] demonstrated to be successful in synovial cell sarcoma.&rdquo; Combo Therapy Tackles Challenges, Adds Clinical Benefits Immune checkpoint inhibitors (ICIs), which target coinhibitory checkpoint receptors CTLA-4 or the PD-1/PD-L1 axis, have demonstrated remarkable clinical activity in many cancers; however, despite their unprecedented success, response to ICIs is neither universal nor uniform. &ldquo;Less than half of the patients respond to treatment with ICI monotherapy and many cancers lack the baseline immunogenicity and/or immune checkpoint pathway proteins necessary for susceptibility to immunotherapy, resulting in dramatic variations in response rates (5% to ~90%) across tumor types,&rdquo; said Leisha Emens, MD, PhD, professor of medicine and director of translational immunotherapy at the Women&rsquo;s Cancer Research Center, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania. &ldquo;Finding a way to bring the benefit to more patients and convert nonresponders to responders, finding a way to rescue patients who progress, and extending and deepening the response are all high-priority goals for research. Finding ways to overcome these challenges will allow us to bring the survival benefit of immunotherapy to more patients,&rdquo; she said. Emens, who will be focusing on combination immunotherapies in her presentation during SITC 2019, noted that these reasons underlie the rationale for exploring combination immunotherapies. In addition, she stated that combinations can help harness tumor biology and integrate immune-targeted therapies with historical treatment modalities, such as radiation and chemotherapy, to provide synergistic benefits to patients.

A Framework to Design Rational Combinations With Immunotherapy Agents

Speaking to the foundational premise of combination immunotherapies, Emens said, &ldquo;Many improvements can be made with immunotherapy combinations, and the combination modalities should be based on the mechanism of induction of the antitumor immune response.&rdquo; She elaborated on how this response has been described with the &ldquo;cancer immunity cycle,&rdquo; a series of stepwise events that must be initiated, progress, and expand iteratively.

&ldquo;If you understand which [step or steps are] defective in a given patient&rsquo;s tumor, then you can design combinations that fill the gap and let the immune cycle be completed. If this design is predicated on underlying mechanisms and is clinically sustained, the combination can perform as a self-perpetuating cycle, where the T-cell response continues until the tumor is eliminated,&rdquo; Emens said. Current and emerging evidence support further development of combinations of immunotherapies, including ICIs, with other therapies or agents as well as other immunotherapy agents in the same class or different classes. For instance, the addition of pembrolizumab (Keytruda), an antiPD-1 antibody, to standard chemotherapy with pemetrexed and a platinum-based drug resulted in significantly longer overall survival (OS; 12-month OS, 69.2% vs 49.4%; HR for death, 0.49) and progressionfree survival (PFS; 8.8 vs 4 months) than chemotherapy alone in patients with previously untreated metastatic nonsquamous non&ndash;small cell lung cancer (NSCLC) without EGFR or ALK mutations.

Similarly, the combination of radiation therapy, which can promote the activation of antitumor T cells, thereby augmenting sensitivity to subsequent immunotherapy, with CTLA-4 blockade with ipilimumab (Yervoy), improved responses in chemotherapy-refractory metastatic NSCLC where antiCTLA-4 antibodies had failed to demonstrate significant efficacy alone or in combination with chemotherapy.

Further, combining 2 different ICIs, nivolumab (Opdivo) and ipilimumab, improved PFS, OS, and overall response rates versus ipilimumab alone in patients with advanced melanoma.

Emens outlined data from combination immunotherapy studies that are coupling immunotherapy agents to novel drugs and therapies, predicated on optimizing the anti-tumor immune response based on tumor-, disease-, and mechanism-specific features. Rational, mechanism-based, novel combinations can help overcome resistance, relapse, or progression after immunotherapyas in a recent study of a combination of pembrolizumab and intratumoral SD-101, a synthetic cytosine-phosphate-guanosine (CpG) oligonu that stimulates Toll-like receptor 9 (TLR9) in patients with unresectable or metastatic malignant melanoma. Early data showed that this combination was well tolerated and induced immune activation at the tumor site, without additional toxicity over pembrolizumab alone.24 Other examples of pioneering combinations mentioned by Emens include pembrolizumab with epacadostat in patients with advanced solid tumors

; nivolumab in combination with ALT-803, an interleukin-15 superagonist, in metastatic NSCLC

; and oncolytic virotherapy with talimogene laherparepvec (Imlygic) in combination with pembrolizumab in advanced melanoma.

&ldquo;My goal is to review the combination of immunotherapies and their importance and provide a framework for how to think about developing innovative combinations,&rdquo; said Emens of her presentation. Some of the key factors to consider in development of immunotherapy combinations include setting clear parameters to define the clinical activity of a combination immunotherapy relative to the activity of either single agent in the context of the tumor type in which it is being tested; evaluating pharmacodynamic changes with agnostic and high-throughput systems-biology technologies; and accounting for the effect of treatment context, drug dose, and treatment sequencing. Emens notes that while combination immunotherapies may help expand the numbers of patients deriving benefit from immunotherapy, it is also important to consider the potential for unexpected and/or synergistic toxicities with these combinations.

The development of immunotherapeutic agents has transformed the treatment landscape of cancer across cancer types and yielded remarkable clinical benefits in responding patients, including those with advanced cancers previously thought to be intractable or difficult to treat. As the field matures, there is great optimism for the range of therapies in use or in development for recruiting the body&rsquo;s immune system to the anticancer combat.

&ldquo;I think that immune cell therapy is important and T cell therapy is very exciting. I predict that it is an area that will be growing in importance in coming years for all cancers,&rdquo; said Hwu. He alluded to ongoing investigations to identify biomarkers predictive of response to TIL therapy as another avenue of growth in immunotherapy.

Emens expressed similar optimism: &ldquo;I believe that we will be able to make immunotherapy work for almost any tumor. If you understand the immunobiology of that specific tumor, you can design ways of eliminating it that capitalize on the antitumor response.&rdquo; She added, &ldquo;The development of combinations should consider the immunobiology of the patient&rsquo;s tumor, the mechanism of each agent, and how they might interact when given together.

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Krithika Subramanian , PhD | Authors

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