Evolving Paradigms in Immuno-Oncology: Treatment Strategies and Clinical Evidence for Checkpoint Inhibition

Treatment Strategies and Clinical Evidence for Checkpoint Inhibiton

Melanoma

Melanoma is an aggressive and potentially fatal form of skin cancer that accounts for the majority (76.9%) of the 13,000 skin cancer-related deaths in the United States each year, even though it accounts for less than 2% of total skin-related cancers.^2,5It is the fifth most common cancer among men (1 in 38 lifetime risk in Caucasian men) and the seventh among women (1 in 58 lifetime risk in Caucasian women).⁴⁸The incidence of melanoma has been increasing exponentially for the past 80 years with an overall, age-adjusted incidence rate of 19.7 per 100,000 as of 2011 (95% CI, 19.5-19.9) and an estimated 74,000 cases in 2015 (up from 65,675 invasive melanoma cases reported in 2011).^5,48,49Centers for Disease Control and Prevention (CDC) data gathered from 1999 to 2011 indicate that there is an increasing incidence with age, until about the age of 70, and that Caucasians account for the vast majority of all melanoma cases in the United States.^16,50The National Cancer Institute (NCI) Surveillance, Epidemiology, and End Result (SEER) Program data from 2005 to 2011 indicates that the 5-year survival rates based on stage at diagnosis are 98.3% for localized melanoma, 63% for regional, 16.6% for distant, and 80.2% for unstaged melanoma.⁵¹Prognosis for patients with stage IV melanoma is very poor, and the 1-year survival rate is only 25%, implicating extended survival as the primary goal of treatment whenever possible.¹⁴

Up to 90% of melanomas are caused by ultraviolet (UV) radiation but additional important risk factors include: personal or family history, weakened immune system (resulting from illness or immunosuppressive medications), dysplastic or other nevi count (atypical moles or birthmarks), xeroderma pigmentosum (XP; an inherited trait rendering the skin incapable of repairing damage by UV radiation), age, gender, occupation, recreation and vacation habits, and diet.^5,14,48,52The over-activating BRAF V600E mutation is the most common mutation associated with melanoma, found in up to 65% of cases and resulting in over 700 times the regular activity of BRAF kinase.⁵³This is a somatically derived missense substitution of glutamic acid for valine at codon 600 of the BRAF gene (B-Raf proto-oncogene, serine/threonine kinase), a protein-coding gene in the RAF/MIL family that is directly involved in regulation of the mitogen-activated protein kinase (MAPK) signal cascade mediation of cellular division and differentiation.^53,54Less prominent, but still prevalent, and possibly a valuable biomarker are somatically derived mutations of the NRAS gene. NRAS mutations are reported in up to 20% of melanoma cases.^53,55

For early-stage nonmetastatic melanomas, wide surgical excision is often sufficient. For more advanced metastatic melanoma, targeted and systemic therapies are often used.⁵CTLA-4 blockade with ipilimumab monotherapy is capable of inducing objective responses in approximately 5% to 15% of patients with metastatic melanoma.²Regardless of BRAF V600 mutation status, immunotherapies (ie, ipilimumab, nivolumab, or pembrolizumab) are recommended systemic therapy by the National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology for all cases of stage III in-transit or stage IV metastatic or unresectable melanomas.⁵⁶Ipilimumab, pembrolizumab, and nivolumab are currently FDA-approved for treatment of melanoma (TABLE 3).

Ipilimumab for Melanoma

Ipilimumab (Yervoy, Bristol-Myers Squibb) is currently indicated for the treatment of unresectable or metastatic melanoma, as well as in the adjuvant treatment of patients with cutaneous melanoma with pathologic involvement of regional lymph nodes of more than 1 mm who have undergone complete resection, including total lymphadenectomy.¹⁶Ipilimumab was approved in 2011 following a randomized, phase III study of 676 patients with unresectable stage III or IV melanoma who had received previous therapy with one or more of the following: dacarbazine, temozolomide, fotemustine, carboplatin, or IL-2. Patients were 18 years of age or older, with an average age of 56 years; 59% were male, and patients were included if they had a life expectancy of at least 4 months, Eastern Cooperative Oncology Group (ECOG) status of 0 or 1 (indicating fully active, in predisease performance status [PS] or restricted in physically strenuous activity but ambulatory and able to do light work of a sedentary nature, respectively), HLA-A*0201 positivity, normal hematologic, hepatic, and renal function, and had not received systemic treatments for 28 days prior to the study. Between September 2004 and August 2008, patients were randomly assigned 3:1:1 to receive either an induction course of ipilimumab 3 mg/kg plus gp100 peptide vaccine at a dose of 1 mg (n = 403), ipilimumab 3 mg/kg plus gp100 placebo (n = 137), or gp100 1 mg plus an ipilimumab placebo (n = 136). All treatments were administered once every 3 weeks for four treatments.¹⁷

The median OS (primary endpoint) in ipilimumab plus gp100 compared with gp100 alone was 10.0 months (range 95% CI, 8.511.5) versus 6.4 months (95% CI, 5.5-8.7) (HR for death, 0.68; P <.001). Median OS for the ipilimumab monotherapy group was 10.1 months (95% CI, 8.0-13.8; HR for death compared with gp100 alone, 0.66, P = .003). There was no difference in OS noted between the two ipilimumab groups. The highest percentage of patients with an objective response was in the ipilimumab monotherapy group (25%; n/N = 2/8) and stable disease (SD) was detected in 52.2% (12/23) of patients in the ipilimumab plus gp100 group. The rates of OS in the ipilimumab plus gp100 group, the ipilimumab monotherapy group, and the gp100 monotherapy group were 43.6%, 45.6%, and 25.3% at 12 months, respectively, and 21.6%, 23.5%, and 13.7% at 24 months, respectively. AEs were detected in 98.4% (374/380), 96.9% (127/131), and 97.0% (128/132) of patients in the combination, ipilimumab monotherapy, and gp100 monotherapy groups, respectively. The most common AEs related to ipilimumab were irAEs, which occurred in approximately 60% of patients treated with ipilimumab and 32% of patients treated with gp100. Grade 3 or 4 irAEs were observed in 10% to 15% of patients treated with ipilimumab and 3% of the patients treated with gp100. All irAEs occurred during the induction period, most commonly affecting the skin and gastrointestinal tract. The most common irAE was diarrhea occurring in 27% to 31% of patients treated with ipilimumab. The average time to resolution for grades 2, 3, or 4 AEs was 6.3 weeks (95% CI, 4.3-8.4) in the ipilimumab plus gp100 group, 4.9 weeks (95% CI, 3.1-6.4) in the ipilimumab group, and 3.1 weeks (95% CI, 1.1 to not reached) in the gp100 group. Ongoing AEs after 2 years included rash, pruritus, diarrhea, anorexia, and fatigue, generally grade 1 or 2. Fourteen deaths (2.1%) were related to the study drugs, and one-half of these were associated with irAEs. Overall the study demonstrated ipilimumab, either alone or in combination with gp100, had the potential to improve OS in patients with metastatic melanoma who had undergone previous treatment.¹⁷

A second randomized, double blind, phase III trial has since led to the approval of ipilimumab as an adjuvant treatment following complete resection of stage III melanoma. Between July 10, 2008, and August 1, 2011, 951 patients with advanced melanoma, histologically confirmed metastatic to the lymph nodes only, were randomly assigned (1:1) to receive ipilimumab 10 mg/kg every 3 weeks for 4 doses, then every 3 months for a maximum of 3 years, or until disease recurrence, unacceptable toxicity, major protocol violation, or treatment refusal of placebo. Patients included in the study were 18 years of age or older, with a median age of 51 years (18-84). More than half (62%) were male, 99% were white, and all patients had an ECOG PS of 0 or 1 (94% had ECOG PS of 0). A total of 20% of patients had stage IIIA melanoma with lymph nodes >1mm, 44% had stage IIIB, and 36% had stage IIIC with no in-transit metastases. The primary endpoint was recurrence-free survival (RFS; time between date of randomization and date of first recurrence of local, regional, or distant metastasis or death). Secondary endpoints included distant metastasis-free survival, OS, AEs, and health-related quality of life.⁵⁷

RFS was significantly longer in the ipilimumab group compared with the control group, with a median RFS of 26.1 months (95% CI, 19.3-39.3) versus 17.1 months (95% CI, 13.4-21.6), respectively. Of the 471 patients who were treated with ipilimumab, 245 (52%) discontinued treatment due to AEs, of which 230 (49%) were drug related. A total of 39% (n = 182) of patients treated with ipilimumab discontinued treatment within the first 12 weeks due to AEs. In the placebo group, 20 patients (n = 4) discontinued due to AEs. Overall, 99% (n = 465/471) of patients in the ipilimumab group had an AE of any grade, with grade 3 or 4 reported in 254 (54%) of patients. In the placebo group, 91% (n = 432/474) of patients experienced AEs of any grade, with grade 3 or 4 in 118 (25%) patients. The most common grade 1 or 2 AEs (present in greater than 10% of participants) in both the treatment and placebo group were diarrhea, fatigue, headache, and nausea (along with abdominal pain and colitis in the treatment group but not the placebo group). The most common grade 3 or 4 AEs in the ipilimumab treatment group were diarrhea and colitis. The most common irAEs in the treatment group were dermatological (rash and pruritis), gastrointestinal (diarrhea and colitis), endocrine (hypophysitis and hypothyroidism), and hepatic (liver function test increase), all of which were present at grade 1 or 2 in greater than 10% of patients receiving treatment (except colitis which was only experienced in 8%). Overall, these data demonstrate that adjuvant ipilimumab treatment in patients with highrisk, stage III melanoma with adequate resection of lymph nodes can significantly improve RFS.⁵⁷

Pembrolizumab for Melanoma

Pembrolizumab (Keytruda, Merck), approved in 2014, was the second checkpoint inhibitor approved for the treatment of melanoma. Pembrolizumab is a PD-1—blocking mAb that is currently indicated for the treatment of patients with unresectable or metastatic melanoma and disease progression following ipilimumab and, if BRAF V600-mutation positive, a BRAF inhibitor.²³Pembrolizumab is believed to decrease tumor growth by releasing PD-1 pathway inhibition of the immune response, including the antitumor immune response, through binding to the PD-1 receptor on T cells and blocking its interaction with PD-L1 and PD-L2.²³Between August 28, 2012, and April 5, 2013, the efficacy of pembrolizumab for the treatment of advanced melanoma was investigated in 173 patients in an open-label, randomized (1:1), dose comparison cohort of the phase I KEYNOTE-001 trial. The median age of patients in the study was 61 years. A total of 60% of patients were male, 97% white, and 66% and 34% had an ECOG PS of 0 and 1, respectively. Patients were randomized to receive either 2 mg/kg (n = 89) or 10 mg/kg (n = 84) intravenous (IV) pembrolizumab every 3 weeks until unacceptable toxicity or disease progression that was symptomatic, rapidly progressive, required urgent intervention, occurred with a decline in PS, or was confirmed at 4 to 6 weeks with repeat imaging. Tumor status assessment was performed every 12 weeks. The primary endpoint was overall response rate (ORR) assessed by RECIST v1.1 and by irRC. ORR was defined as the percentage of patients who achieved a best overall response of complete or partial response. Important secondary endpoints included response duration, PFS, and OS.58

Coincidentally, the ORR was 26% (n = 21; 95% CI, 17-37) in the 2 mg/kg group and 26% (n = 20; 95% CI, 17-38) in the 10 mg/kg group (difference 0%; 95% CI, —14 to 13; P = .96). Within each group there was one complete response (CR) and a 25% partial response (PR) rate. Reduction in baseline lesion size was observed in 59 (73%) patients in the 2-mg/kg group and 52 (68%) in the 10-mg/kg group. Median PFS by independent central review was 22 weeks (95% CI, 12-36) for the pembrolizumab 2-mg/kg group and 14 weeks (95% CI, 12-24) for the pembrolizumab 10-mg/kg group (HR 0.84, 95% CI 0.57-1.23). Median PFS by irRC was 31 weeks in the pembrolizumab 2-mg/kg group and 35 weeks in the 10-mg/kg group.58 The overall safety profiles were similar in both groups. Drug-related AEs occurred in 73 (82%) patients in the 2-mg/kg group and 69 (82%) patients in the 10-mg/ kg group. In the 2-mg/kg group compared with the 10-mg/kg group, grade 3 or 4 drug-related AEs occurred in 13 (15%) versus 7 (8%) patients, respectively, with fatigue being the only AE experienced by more than one patient. Serious irAEs occurred in only 4 (2%) patients. Anemia of any grade occurred in 55% of patients receiving 2 mg/kg, with 8% experiencing grade 3 to 4 anemia.⁵⁸

Nivolumab for Melanoma

Similar to pembrolizumab, nivolumab (Opdivo, Bristol-Myers Squibb) is an anti—PD-1 mAb that is currently indicated for the treatment of unresectable or metastatic melanoma, as a single agent in patients with disease progression following ipilimumab and, if BRAF V600-mutation positive, a BRAF inhibitor. It is also approved in combination with ipilimumab in patients with BRAF V600 wildtype (WT) melanoma. Nivolumab functions by binding to the PD-1 receptor, blocking its interaction with ligands, PD-L1 and PD-L2, and thereby releasing PD-1 pathway-mediated inhibition of the immune response, including the antitumor immune response.²⁴

Nivolumab was approved for the treatment of melanoma in 2014 following the pivotal CheckMate 037 trial (a randomized, controlled, open-label, phase III trial of nivolumab compared with investigator&rsquo;s choice chemotherapy [ICC] in patients with advanced melanoma who progressed after anti—CTLA-4 treatment). Between December 21, 2012, and January 10, 2014, patients were screened and randomized (2:1) to receive either nivolumab 3 mg/kg every 2 weeks (n = 272) or ICC (n = 133; either dacarbazine 1000 mg/m2 every 3 weeks, or carboplatin area under the curve 6 plus paclitaxel 175 mg/m2 every 3 weeks). Randomization was further stratified by PD-L1 expression status, BRAF V600-mutation status, and demonstrated clinical benefit from previous ipilimumab treatment. In the nivolumab treatment group, patients were an average age of 59 years (23-88), 65% were male, 49% were pretreatment PD-L1&minus;positive, 22% were BRAF mutation-positive, and 60% and 40% had an ECOG status of 0 or 1, respectively. ORR was the primary endpoint.⁵⁹

Overall, confirmed objective response was observed in 38 (31.7%; 95% CI, 23.5-40.8) patients in the nivolumab treatment group versus 5 (10.6%; 95% CI, 3.5-23.1) patients in the ICC group. In terms of best overall response in the nivolumab versus ICC group, CR was observed in 4 (3.3%) patients treated with nivolumab and no patients treated with ICC. Partial response was observed in 34 (28.3%) versus 5 (10.6%), and stable disease was seen in 28 (23.3%) versus 16 (34.0%) nivolumab-treated and ICC-treated patients, respectively.⁵⁹

Treatment-related AEs of any grade occurred in 181 (68%) of 268 patients in the nivolumab group and 81 (79%) of 102 patients in the ICC group. Overall the most common treatment-related AEs were fatigue, pruritus, diarrhea, nausea, and anemia. Grade 3 or 4 treatment-related AEs were observed in 24 (9%) of the 268 patients in the nivolumab group versus 32 (31%) of the 102 patients in the ICC group. In the nivolumab group, the most common grade 3 or 4 AEs included increased lipase in 3 patients (1%), increased alanine aminotransferase, anemia, and fatigue (each affecting 2 patients [1%]). In the ICC group, the most common grade 3 or 4 AEs included neutropenia in 14 patients (14%), thrombocytopenia in 6 patients (6%), and anemia in 5 patients (5%). No treatment-related deaths occurred.⁵⁹

Combination Immunotherapy in Melanoma

Combination of CTLA-4 and PD-1 blockade is currently FDA-approved in the context of nivolumab plus ipilimumab for the treatment of melanoma. In addition, late-phase trials for various other checkpoint inhibitor combinations are under way (TABLE 4). It is a logical and synergistic strategy given that both therapies target separate checkpoints involved in immune suppression. However, it must be considered in the context of increased AEs from multiple agents.

Combination immune checkpoint blockade with nivolumab and ipilimumab was recently evaluated in the phase III study (CheckMate 067) to assess the safety and efficacy compared with either agent alone in previously untreated patients with metastatic melanoma. From July 2013 through March 2014, a total of 945 patients underwent randomization (1:1:1) with 316 assigned to the nivolumab monotherapy group, 314 to the nivolumab plus ipilimumab group, and 315 to the ipilimumab monotherapy group. The treatment regimens, administered by means of IV infusion, were as follows: 3 mg/ kg nivolumab every 2 weeks plus ipilimumab-matched placebo (nivolumab monotherapy group); 1 mg/kg nivolumab every 3 weeks plus 3 mg/kg ipilimumab every 3 weeks for 4 doses, followed by 3 mg/kg nivolumab every 2 weeks for cycle 3 and beyond (combination therapy group); or 3 mg/kg ipilimumab every 3 weeks for 4 doses plus nivolumab-matched placebo (ipilimumab monotherapy group). The mean age in the study was 60 years (18-90), 64.6% of participants were male, 23.6% were PD-L1 positive, 31.5% were BRAF V600 mutation-positive, and 73.2% and 26.6% had an ECOG PS of 0 or 1, respectively (1 individual had ECOG PS of 2 in the nivolumab group).³⁷

The median PFS (primary endpoint) was 11.5 months (95% CI, 8.9-16.7) in the combination therapy group; 2.9 months (95% CI, 2.8-3.4) with ipilimumab monotherapy (HR for death or disease progression, 0.42; 95% CI, 0.31-0.57; P <.001), and 6.9 months (95% CI, 4.3-9.5) with nivolumab monotherapy (HR for the comparison with ipilimumab, 0.57; 95% CI, 0.43-0.76; P <.001). It is noteworthy that in patients with tumors positive for PD-L1, the median PFS was 14.0 months in both the combination group and in the nivolumab monotherapy group. In patients with tumors negative for PD-L1, median PFS was longer with combination therapy than with nivolumab alone (11.2 months [95% CI, 8.0 to not reached] versus 5.3 months [95% CI, 2.8-7.1]). Treatment-related AEs of grade 3 or 4 occurred in 55.0% of patients in the nivolumab plus ipilimumab group, 16.3% in the nivolumab monotherapy group, and 27.3% in the ipilimumab monotherapy group. Any grade AE occurred in 99.7%, 99.4%, and 99.0% of patients in each group, respectively. From the data it can be seen that nivolumab alone or in combination with ipilimumab resulted in significantly longer PFS than ipilimumab alone and that the combination resulted in greater overall AEs.³⁷These results led to the FDA approval of nivolumab in combination with ipilimumab for patients with BRAF V600 wild-type (WT) melanoma.²⁴It is also significant that in patients with PD-L1—negative tumors, the combination of ipilimumab and nivolumab was more effective than either agent alone. As such, the use of PD-L1 as a biomarker may allow clinicians to make more informed decisions about risk-benefit ratios for combination therapy versus monotherapy.³⁷

Further evidence for the use of combination therapy has been demonstrated in an ongoing phase II, dose escalation study (CheckMate 069; NCT01927419) assessing ipilimumab plus nivolumab therapy in previously untreated patients with advanced melanoma (n = 142) with or without the BRAF mutation. In this study, patients with BRAF WT tumors (BRAF V600 mutation-free) demonstrated an ORR of 61% (n = 44/72) in the combination therapy group versus 11% (n = 4/37) in the monotherapy group (P <.001), with 16 (22%) CRs in the combination group and no CRs in the monotherapy group. In patients with BRAF WT tumors within the combination group, a 68.1% median decrease in tumor volume was measured versus a 5.5% increase in median tumor volume within the monotherapy group. For these participants, median PFS time was not reached in the combination group compared with 4.4 months (95% CI, 2.8-5.7) with the ipilimumab monotherapy group (HR associated with combination therapy compared with ipilimumab monotherapy for disease progression or death, 0.40; 95% CI, 0.23-0.68; P <.001).61 In patients with BRAFmutation—positive tumors, the median PFS was 8.5 months (95% CI, 2.8 to not estimable) compared with 2.7 months (95% CI, 1.0-5.4) in the ipilimumab monotherapy group (HR, 0.38; 95% CI, 0.15-1.00). In these patients, the nivolumab plus ipilimumab therapy group was observed to have an ORR of 52% (n = 12/23) with a CR rate of 22% (n = 5/23) versus 10% ORR (n = 1/10) and no CR in the monotherapy group. Thus, it was demonstrated that ipilimumab combined with nivolumab compared with ipilimumab alone provided a greater and more durable response rate, longer PFS, and higher rates of CR for patients with advanced melanoma.^61,62

Treatment-related AEs of any grade were comparable in both the combination and monotherapy groups (91% vs 93%). However, treatment-related AEs leading to discontinuation of treatment was substantially greater in the combination group versus monotherapy (47% vs 17%) and the occurrence of grade 3 or 4 drug-related AEs was also higher (54% vs 24%, respectively).61 In light of safety profiles and differences in efficacy, considerations must be made for the combination of CTLA-4 and PD-1 blockade provided by ipilimumab and nivolumab when compared with CTLA-4 alone, in patients with advanced melanoma.

Additional combinations of checkpoint inhibitors for the treatment of melanoma are also being investigated. As mentioned previously, the anti—PD-L1 antibody durvalumab (MEDI4736; AstraZeneca) is a human IgG1 mAb that blocks PD-L1 from binding to PD-1 and B7-1 (CD80) with high affinity and selectivity. It has demonstrated clinical activity and durable response with an acceptable safety profile in multiple tumor types. Durvalumab is currently being assessed in a phase I/II study (NCT02027961) in combination with BRAF and/or MEK inhibitors (dabrafenib and trametinib, respectively) versus trametinib alone in advanced metastatic melanoma.⁶³Durvalumab was administered at either 3 or 10 mg/kg (IV every 2 weeks) in combination with dabrafenib 150 mg twice daily plus trametinib 2 mg daily versus trametinib 2 mg daily alone in patients with stage IIIc/IV melanoma. As of December 2014, 50 patients have been treated. In patients receiving the triple combination with 3 mg/kg durvalumab (n = 6), AEs were reported in 100% of cases, with grade 3 or greater in 17% of patients treated. Objective response was observed in 6/6 (100%) of patients treated with 3 mg/kg durvalumab in the triple combination, with PR or CR in all instances. For patients receiving the triple combination with 10 mg/kg durvalumab (n = 18), AEs were reported in 94% of cases, with grade 3 or greater in 39%. Objective response in this group was observed in 10/15 (67%) patients, and stable disease in 5/15 cases. For patients receiving 10 mg/kg durvalumab plus trametinib (n = 20), AEs were noted in 90% of cases, with grade 3 or greater in 40% of patients. ORR was 21% (3/14), and stable disease in 6/14 cases. For patients receiving sequential trametinib plus durvalumab 10 mg/kg (n = 6), AEs were reported in 100% of cases, with grade 3 or more in 17% of patients. ORR was observed in 50% (3/6) of patients, and stable disease in 1/6 cases.⁶⁴

Biomarkers and Diagnostic Factors for Melanoma

Certain biomarkers have shown to be important for the selection of patients with melanoma who may benefit most from PD-1-/PDL1—blockade therapy. Specifically, PD-L1 has been identified as a biomarker that indicates which patients may benefit most from anti&ndash;PD-1/PD-L1 treatment. The CheckMate 002 study, a phase II randomized, controlled comparative trial of pembrolizumab versus chemotherapy in patients (n = 421) with ipilimumabrefractory advanced melanoma, revealed that PD-L1 is a positive prognostic biomarker for efficacy with pembrolizumab treatment. Analysis of data from this trial demonstrated differential efficacy based on PD-L1 expression, specifically that in patients with PDL1&ndash;positive tumors (n = 291), pembrolizumab treatment (n = 193) is associated with a significantly higher ORR (26% [95% CI, 2033] versus 4% [95% CI, 1-10]), and increased 6-month PFS (40% vs 13%) compared with chemotherapy treatment (n = 98). When compared with patients having PD-L&ndash;negative tumors (n = 130) treated with pembrolizumab (n = 93) versus chemotherapy treatment (n = 37), the observed ORR was 15% (95% CI, 8-24) compared with 8% (95% CI, 2-22), respectively, and the 6-month PFS was 26% versus 22%, respectively. Even though all patients treated with pembrolizumab demonstrated improvement in this study, patients with PD-L1&minus;positive tumors responded more robustly than did those with PD-L1&minus;negative tumors.38 A minimal presence or complete absence of PD-L1 may also be useful in guiding treatment selection. In the CheckMate 067 (NCT01844505) study it was observed that patients with PD-L1&minus;negative tumors achieved the greatest benefit from a combination of ipilimumab and nivolumab compared with either agent alone. Due to this, and in consideration of risk-benefit analysis, the use of anti&ndash;CTLA-4 and anti&ndash;PD-1 combination therapies in instances of patients with PDL1&minus;negative tumors may be more beneficial than monotherapy compared with instances of patients with PD-L1&minus;positive tumors, in which case the benefit from PD-1/PD-L1 blockade may provide adequate results without the added risk of additional agents.³⁷Bim, a downstream biomarker of PD-1/PD-L1 interaction, is another potential indicator of efficacy for PD-1/PD-L1 therapy. Bim is found to be present at significantly higher levels in patients with metastatic melanoma, and elevated Bim levels have been associated with decreased OS compared with patients with lower levels (8.9 months vs 13.8 months; P < .01). As such, the use of Bim as a biomarker may aid in the identification of patients who could benefit from PD-1—/PD-L1&ndash;blockade therapy.³⁹

As mentioned, NRAS mutation status may also prove helpful in predicting benefit of PD-1/PD-L1 pathway blockade therapies in melanoma. According to a retrospective study of 229 patients with melanoma receiving immunotherapy as a primary, secondary, or tertiary treatment, including 28 (28%) patients receiving anti—PD-1 /PD-L1 as first-line therapy and 20 (36%) patients receiving it as a secondary treatment, NRAS mutation-positive patients (n = 11) achieved greater benefit from treatment compared with patients without the mutation (73% [n = 8/11] vs 43% [n = 10/23]), respectively. ORR was 64% (n = 7/23) compared with 35% (n = 8/23), respectively. When compared with patients in the same study who received ipilimumab (NRAS-mutation&ndash;positive, n = 43; WT, n = 95) or IL-2 treatment (NRAS-mutation&ndash;positive, n = 15; WT, n = 19), anti&ndash; PD-1/PD-L1 therapy was still the most effective treatment option for both NRAS-mutation&ndash;positive and mutation&ndash;negative patients (ORRs for ipilimumab treatment, 19% [n = 8] and 11% [n=11], with clinical benefit in 42% [n = 18] and 20% [n = 19]; ORRs for IL-2 treatment, 33% [n = 5] and 26% [n=5], respectively). Thus, NRAS mutation is a distinct cohort within the disease, correlating to poor prognosis, and NRAS mutation status may be used as a selection factor for determining which patients are optimal candidates for anti&ndash;PD-1 treatment.⁴⁴

Large-scale analysis of biomarkers in patients with melanoma treated with ipilimumab has also uncovered that the rate of increase in ALC is correlated with clinical benefit. Through retrospective analysis of pooled data from three studies of patients with unresectable stage III/IV melanoma (379 patients), a positive correlation between greater ALC change and evidence of clinical activity was uncovered (P = .0013). This correlation was then confirmed in a prospective fashion in 64 additional patients (P = .00042).⁴⁶A second study of 51 patients has also confirmed the significance of ALC. Patients with ALC &ge;1000 cells/&mu;L after the second dose of ipilimumab had a higher rate of clinical benefit at week 24 (52% vs 0%; P = .01). Similarly, the high ALC group also had greater rates of 6-month (75% vs 0%) and12-month (47% vs 0%) OS.47 This indicates that there is an ALC threshold (1000 cells/&mu;L) and that patients with an ALC count below this threshold may not benefit from further treatment with ipilimumab.⁴⁷

Non—Small Cell Lung Cancer (NSCLC)

Lung cancer is the number one cause of cancer deaths (accounting for 27%), with an estimated 158,000 deaths in the United States in 2015.13,50,65 An estimated 221,200 new cases were expected in the United States in 2015, accounting for 13.3% of new cancer cases.66 Roughly 65% of lung cancer diagnoses are made in individuals over 65 years of age, with an average of 70 years at time of diagnoses. Eight out of ten lung cancer cases are a result of smoking, but other important risk factors include exposure to radon, asbestos, air pollution, arsenic in drinking water, and a family history of lung cancer. The overall lifetime risk of developing lung cancer is 1 in 13 for men and 1 in 16 for women with numbers much higher for smokers than for nonsmokers.⁶⁵Based on SEER data from 1998 to 2000, the 5-year survival for lung cancer by stage is 49% for stage IA, 45% for stage IB, 30% for stage IIA, 31% for stage IIB, 24% for stage IIIA, 5% for stage IIIB, and 1% for stage IV.⁶⁵

NSCLC is the most common type of lung cancer, accounting for 85% to 90% of all lung cancer cases. PD-L1 and PD-L2 have been shown to be upregulated in NSCLC allowing for immune evasion and inhibition of antitumor response.⁶⁷The main treatment options for NSCLC include surgery, radiofrequency ablation, radiation therapy, chemotherapy, targeted therapy, and immunotherapy. In most cases, more than one type of treatment will be used.65 Treatment depends on tumor histology and presence of epidermal growth factor receptor (EGFR) mutation or anaplastic lymphoma kinase (ALK) rearrangements.68 The NCCN recommends (category 1) the use of systemic immune checkpoint inhibitors (nivolumab, or in the case of PD-L1 expression, pembrolizumab) for patients with metastatic nonsquamous NSCLC who have progressed on or after platinumbased chemotherapy.69 Nivolumab and pembrolizumab are both approved for the treatment of NSCLC (TABLE 5).

Nivolumab in NSCLC

Nivolumab was granted extended approval in March 2015, for the treatment of metastatic squamous NSCLC with progression on or after platinum-based chemotherapy.²⁴Key trials that led to this approval include CheckMate 017 and CheckMate 057. CheckMate 017 was a phase III trial of nivolumab versus docetaxel, involving 272 patients with stage IIIB or IV squamous cell NSCLC who had disease recurrence after one prior platinum-containing regimen. Patients underwent randomization from October 2012 through December 2013 to receive nivolumab 3 mg/kg every 2 weeks (n = 135) or docetaxel 75 mg/m2 every 3 weeks (n = 137). The median age of participants was 63 years (39-85), 92% (n = 250) of patients were current or former smokers, 76% were male, and 24% and 76% had ECOG PS score of 0 or 1, respectively. Among the 272 patients in the study, 225 (87%) had quantifiable PD-L1 expression. These individuals were balanced between treatment arms. The primary endpoint was OS, and secondary endpoints included efficacy based on PD-L1 expression.⁷⁰

Similar ORRs were observed among patients with PD-L1—positive tumors compared with patients who had PD-L1&ndash;negative tumors, and were consistently higher with nivolumab treatment than with docetaxel treatment. The median OS was 9.2 months (95% CI, 7.313.3) in the nivolumab group versus 6.0 months (95% CI, 5.1-7.3) in the docetaxel group. The risk of death was 41% lower in the nivolumab group (HR, 0.59; 95% CI, 0.44-0.79; P <.001), and OS was significantly longer with a 1-year survival rate of 42% (95% CI, 34-50) in the nivolumab group versus 24% (95% CI, 17-31) in the docetaxel group. Treatment-related AEs of any grade were reported in 76 (58%) of patients treated with nivolumab compared with 111 (86%) treated with docetaxel, and grade 3 or 4 AEs were reported in 9 (7%) versus 71 (55%), respectively. The most commonly reported AEs were fatigue, decreased appetite, asthenia, nausea, and diarrhea. The most common grade 3 or 4 AEs were fatigue, decreased appetite, and leukopenia, each present in 1% (n = 1/131) of patients.⁷⁰

CheckMate 057 was a phase III, randomized, open-label study in which 582 patients with stage IIIB or IV or recurrent nonsquamous NSCLC after radiation therapy or surgical resection, who also had disease recurrence or progression during or after one prior platinumbased doublet chemotherapy regimen, were randomized to receive therapy from November 2012 to December 2013. Patients received nivolumab 3 mg/kg every 2 weeks (n = 292) or docetaxel 75 mg/m2 every 3 weeks (n = 290). The average age of patients was 62 years (21-85), with 79% current or former smokers, 55% males, and 31% and 69% having an ECOG performance score of 0 or 1, respectively. Among the 582 patients in the study, 455 (78%) had quantifiable PD-L1 expression. The primary endpoint was OS. Efficacy according to PD-L1 expression was among the secondary endpoints.⁷¹

At the time of interim analysis (March 18, 2015; minimum of 13.2 months follow-up) there was a strong predictive association between PD-L1 expression and clinical outcome. Still, independent of PD-L1 expression, OS was found to be significantly longer in thenivolumab treatment group (median OS of 12.2 months [95% CI, 9.7-15.0]) compared with docetaxel (9.4 months [95% CI, 8.1-10.7]), representing a 27% lower risk of death with nivolumab (HR, 0.73; 96% CI, 0.59-0.89; P = .002). The 1-year OS rates were found to be 51% (95% CI, 45-56) with nivolumab versus 39% (95% CI, 33-45) with docetaxel. Treatment-related AEs of any grade occurred in 199 (69%) patients in the nivolumab treatment group versus 236 (88%) patients in the docetaxel group, and grade 3 or 4 AEs occurred in 30 (10%) versus 144 (54%), respectively. The most common treatmentrelated AEs included fatigue, nausea, decreased appetite, asthenia, and diarrhea. The most common grade 3 or 4 AEs were fatigue, nausea, and diarrhea.⁷¹

Nivolumab is currently slated to be studied in a preoperative setting in patients with resectable NSCLC in a phase II clinical trial (NCT02259621) that is recruiting participants (estimated enrollment of 16 participants; last updated October 2015). Safety is the primary endpoint of the study.⁷²

Pembrolizumab in NSCLC

Pembrolizumab has also demonstrated clinical benefit for the treatment of NSCLC and approval was recently extended (under accelerated review) to include treatment of patients with metastatic NSCLC whose tumors express PD-L1 (as determined by an FDA-approved test [eg, IHC 22C3 pharmDxTM Kit]) and who have disease progression on or after platinum-containing chemotherapy.²³The efficacy of pembrolizumab was studied in a subgroup of the 280 patients from the Keynote 001 phase I, open-label multicohort, activity-estimating study consisting of 495 patients with metastatic NSCLC who had progressed following platinum-containing chemotherapy, and if appropriate, targeted therapy for ALK or EGFR mutations.26 Retrospective analysis was then performed in a prospectively defined subgroup consisting of 61 patients with a demonstrated PD-L1 expression tumor proportion score (TPS) of greater than or equal to 50% tumor cells as determined by the PD-L1 IHC 22C3 pharmDxTM Kit.²³Patients in this subgroup received pembrolizumab 10 mg/kg every 2 (n = 27) or 3 (n = 34) weeks until unacceptable toxicity or disease progression that was symptomatic, was rapidly progressive, required urgent intervention, occurred with a decline in PS, or was confirmed at 4 to 6 weeks with repeat imaging. Assessment of tumor status was performed every 9 weeks. The primary endpoint was ORR.

The average age of participants was 60 years (with 34% aged 65 or older), 61% were male, and 34% and 64% had an ECOG PS of 0 or 1, respectively. The majority of cases (75%) were nonsquamous NSCLC, with 21% squamous NSCLC. Among the 61 subjects, an ORR was observed in 25 (41%; 95% CI, 29-54); all responses were partial. At the time of final analysis of ORR, 21 (84%) patients had ongoing responses and 11 (44%) of these patients had ongoing responses for 6 months or longer.²³AEs occurred in 70.9% (351/495) of the larger patient cohort, with grade 3 or 4 occurring in 9.5% (47/495) of patients. The most common AEs were fatigue, pruritus, decreased appetite, rash, arthralgia, diarrhea, and nausea. The most common grade 3 or greater AEs were dyspnea, pneumonitis, decreased appetite, fatigue, and nausea. Of note, dyspnea and pneumonitis of grade 3 or greater were observed in 3.8% (19/495) and 1.8% (9/495) of patients, respectively, with one pneumonitis-related death.²⁶

Investigational and Combination Therapies in NSCLC

Durvalumab (MEDI4736; AstraZeneca) is an anti—PD-L1 therapy that is currently being investigated in several phase II and phase III trials for use as monotherapy or combination therapy for the treatment of NSCLC (TABLE 6). A phase IIa, open-label, multicenter, multicohort, immune-modulated therapy (IMT) study (NCT02179671) is evaluating the use of selected small molecule therapies (gefitinib, AZD9291 [TAGRISSO; AstraZeneca], or selumetinib + docetaxel) or a first IMT (tremelimumab) with a sequential switch to a second IMT (durvalumab) in patients with locally advanced or metastatic NSCLC (stage IIIB-IV). The study was initiated July 2014 with expected completion in November 2017. The estimated enrollment is 40 patients and the primary objective is to assess the efficacy of various sequences of either a small molecule therapy or an IMT followed by a second IMT (durvalumab) as measured by confirmed CR. Secondary outcome measures include ORR and disease control rate.⁷³

A second phase II trial (ATLANTIC; NCT02087423) is also under way to determine the use of durvalumab as monotherapy in locally advanced or metastatic NSCLC. This study was initiated February 2014 with expected completion in June 2017. The estimated enrollment for this study is 453 patients with documented stage IIIB/IV NSCLC and PD-L1&minus;positive tumors. The study is designed to test the safety, efficacy, and tolerability of durvalumab with the primary endpoint of ORR. Durvalumab is being investigated in a third phase II/III trial in which patients with tumors that do not match one of the currently active drug-biomarker combinations will be randomized to receive IV durvalumab once every 2 weeks for 12 months in the absence of disease progression or unacceptable toxicity. In a phase III, placebo-controlled study (PACIFIC; NCT02125461), durvalumab is being compared with placebo following concurrent chemoradiation in locally advanced, unresectable NSCLC. This study was initiated in May 2014 with expected completion in January 2020. The estimated enrollment for this study is 702 patients, and the primary outcomes are OS and PFS.74

Durvalumab is also being investigated in four additional combination therapy trials, including three assessing the combination of durvalumab plus the anti—CTLA-4 antibody tremelimumab, and one trial assessing adjuvant use of durvalumab postoperatively in completely resected NSCLC. In the phase III open-label, randomized, multicenter ARCTIC study (NCT02352948), durvalumab is being evaluated as a monotherapy or in combination with tremelimumab based on the determination of PD-L1 expression compared with current standard of care (investigator choice of vinorelbine, gemcitabine, or erlotinib) in patients with locally advanced or metastatic NSCLC(stage IIIB/IV) who have at least two prior treatment regimens, including one platinumbased chemotherapy (total estimated enrollment n = 900). Patients are to be stratified by PD-L1 expression to evaluate efficacy of treatment with durvalumab in patients with PD-L1&minus;positive tumors and durvalumab plus tremelimumab combination therapy in patients with PDL1&minus;negative tumors. The primary outcome measures are OS and PFS, and secondary objectives include ORR, duration of response, safety, tolerability, pharmacokinetics, immunogenicity, and health-related quality of life. Tumor assessment is to be performed every 8 weeks for the first 48 weeks, then every 12 weeks. This trial is currently recruiting, and the estimated study completion date is November 2017.⁷⁵

The second study evaluating the combination of durvalumab plus tremelimumab is the phase III, open-label MYSTIC study (NCT02453282). In this randomized, multicenter, global study, 675 immunotherapy/chemotherapy-naïve patients with advanced or metastatic (stage IV) NSCLC (all without EGFR and ALK mutations) will be randomized (1:1:1) to receive either durvalumab 20 mg/kg IV every 4 weeks for up to 12 months plus tremelimumab 1 mg/kg IV every 4 weeks for up to 4 doses (n = 225); durvalumab monotherapy 20 mg/kg IV every 4 weeks for up to 12 months (n = 225); or platinum-based doublet chemotherapy standard of care (n = 225).^76,77Patients will be further stratified by PD-L1 status and histology. The primary endpoint is PFS. Secondary endpoints will include ORR, proportion of patients alive and progression free at 12 months, duration of response, time from randomization to second progression, and OS. Exploratory outcomes will include potential biomarkers of response to treatment assessed on a biopsy at trial entry. This study was started July 2015, is expected to enroll 675 patients, and has an estimated completion date of June 2018.^76,77

The third study evaluating the combination of durvalumab and tremelimumab is the randomized, open-label, phase III NEPTUNE study (NCT02542293). It was designed to determine the efficacy and safety of combination therapy versus platinum-based standardof-care chemotherapy in the first-line treatment of patients with EGFR and ALK WT advanced or metastatic NSCLC. The primary outcome measure for this study is OS, and it is estimated to enroll 800 patients starting in November 2015. NEPTUNE is expected to complete September 2018.⁷⁸

Finally, durvalumab is also being studied as an adjuvant therapy administered after complete resection of NSCLC in a phase III, double-blind, placebo-controlled study (NCT02273375). The purpose of this study is to determine if it is better to receive durvalumab or no therapy following surgical resection of NSCLC based on two treatment arms that are stratified by PD-L1 status. The primary outcome measure is disease-free survival for patients with NSCLC that are PD-L1 positive. This study was initiated in October 2014, expects to enroll 1100 patients, and is estimated to complete in January 2025.⁷⁹

In addition, durvalumab is currently being studied in the randomized, phase II/III study of biomarker-targeted second-line therapy in patients with recurrent stage IIIB/IV squamous cell lung cancer (Lung-Map: S1400; NCT02154490). This study will use biomarkers to determine substudy cancer therapies with the ultimate goal of being able to approve new targeted therapies in this setting. Patients with tumors that do not match one of the currently active drug-biomarker combinations will be randomized to receive durvalumab every 2 weeks for 12 months in the absence of disease progression or unacceptable toxicity. In addition to durvalumab the study will also include treatment arms for the PI3k inhibitor, GDC0032; palbociclib isethionate; the fibroblast growth factor (FGFR) inhibitor AZD4547, rilotumumab, docetaxel, and erlotinib hydrochloride. The study was initiated in June 2014 with an expected completion in June 2022. The expected enrollment for the entire study is 10,000 patients.⁸⁰

Atezolizumab in NSCLC

Atezolizumab (MPDL3280; Genentech) is another anti—PD-L1 antibody currently being evaluated for the treatment of NSCLC. In February 2015, atezolizumab received breakthrough therapy designation from the FDA as a potential treatment for patients with PD-L1&ndash; positive NSCLC following progression on prior therapy, including chemotherapy and targeted therapies.⁸⁴Atezolizumab is also being evaluated in several phase II and III studies (TABLE 7). The efficacy, safety, and predictive biomarker results from the randomized phase II POPLAR study (NCT01903993) comparing atezolizumab (n = 144) versus docetaxel (n = 143) in NSCLC (n = 287) were recently presented. Patients were stratified by PD-L1 expression status (using the SP142 antibody assay) in tumor cells (TCs) and tumor-infiltrating immune cells (ICs) (TC0, 1, 2, or 3 and TIC 0, 1, 2, 3). IV atezolizumab was administered at 1200 mg every 3 weeks and docetaxel was used at 75 mg/m2 every 3 weeks.⁸³

Improved efficacy was observed, correlating with increasing PDL1 expression. In patients with the highest levels of PD-L1 expression in TCs or ICs (TC3 or TIC3), the median OS with atezolizumab (n = 24) was not yet reached compared with 11.1 months with docetaxel (n = 23) (HR 0.47; 95% CI, 0.20-1.11), the median PFS was 9.7 versus 3.9 months (HR 0.56; 95% CI, 0.28-1.11), and ORR was 38% versus 13%. There was no difference in median PFS (9.7 months for both) between treatment groups for patients without PDL1 expression (TC0/IC0). Across all patients (n = 287), the median OS was 11.4 months with atezolizumab treatment (n = 144) versus 9.5 months with docetaxel treatment (n = 143) (HR 0.78; 95% CI, 0.59-1.03). Fewer grade 3 to 5 AEs were observed in the atezolizumab group versus docetaxel group (43% vs 56%).⁸³

In the phase II BIRCH study (NCT02031458), PD-L1&minus;positive patients with advanced metastatic NSCLC will receive 1200 mg atezolizumab IV every 3 weeks for as long as clinical benefit is observed. The primary outcome measure is ORR. This study was initiated January 2014, expects to enroll nearly 670 patients, and is estimated for completion in November 2017. It is not currently recruiting.⁸⁴In the ongoing phase III OAK study (NCT02008227), patients with locally advanced or metastatic NSCLC who have failed platinum-containing chemotherapy are being evaluated for OS after receiving either atezolizumab 1200 mg every 3 weeks or docetaxel 75 mg/m2 every 3 weeks. The study was initiated January 2014, and has an estimated completion date of June 2017. The study expects to enroll 1225 patients.⁸⁵Finally, atezolizumab monotherapy is also being evaluated in a separate phase III study (IMpower 111; NCT02409355) compared with gemcitabine plus cisplatin or carboplatin in chemotherapy-naïve patients with NSCLC (n = 400). This study was initiated in May 2015, and has an estimated completion date of July 2019 over which time patients will receive either atezolizumab 1200 mg every 3 weeks or gemcitabine plus cisplatin or carboplatin. The primary outcome measure is PFS.⁸⁶

Combination therapy with atezolizumab and chemotherapy (carboplatin plus paclitaxel or carboplatin plus nab-paclitaxel) is being investigated in patients with NSCLC (n = 1200) in the phase III IMpower 131 trial (NCT02367794). The study was initiated June 2015, and expects to complete in February 2023. The primarily efficacy measure is PFS.⁸⁷

Avelumab in NSCLC

Avelumab (MSB0010718C; Pfizer/Merck) is a fully-human anti— PD-L1 mAb that is currently in phase III development in an openlabel, multicenter, randomized clinical trial (JAVELIN lung 200; NCT02395172) assessing the efficacy and safety of 10 mg/kg every 2 weeks compared with docetaxel 75 mg/m2 every 3 weeks in patients with stage IIIb/IV or recurrent NSCLC who have experienced disease progression after receiving a prior platinum-containing doublet therapy. The trial was initiated in March 2015 and is expected to extend to October 2021 over which time an estimated 650 patients will be treated. The primary outcome measure is OS.⁸⁹

Biomarkers and Diagnostic Factors in NSCLC

PD-L1 expression has been observed to be a relatively consistent, positive prognostic biomarker in NSCLC, indicating increased treatment success with PD-1 blockade. This was evident in the CheckMate 057 trial when, at the time of interim analysis (March 18, 2015; minimum of 13.2 months follow-up), a strong predictive association between PD-L1 and clinical outcome was observed. This is further evident in the CheckMate 063 trial (a phase II, single-arm trial investigating the activity and safety of nivolumab for patients with advanced, refractory squamous NSCLC).^71,90

In CheckMate 063, 117 patients with documented stage IIIB or IV squamous NSCLC were enrolled between November 16, 2012 and July 22, 2013 to receive nivolumab 3 mg/kg by IV infusion every 2 weeks (1 cycle) until disease progression or unacceptable toxic effects were reached. A total of 76 patients could be assessed for PDL1 expression with 25 (33%) displaying PD-L1&minus;positive tumors. The primary endpoint was ORR.90 Notably, reduction in target tumor lesion burden was significantly greater in patients with PD-L1&minus;positive tumors (n = 13/25; 52%) than in patients with PD-L1&minus;negative tumors (n = 15/40: 38%). Among the 117 patients in the study, ORR was seen in 17 (14.5%; 95% CI, 9-22), with no CRs, partial responses in 17 patients (14.5%; 95% CI, 8.7-22.2), SD in 30 patients (26%; 95% CI, 18-35), and progressive disease in 51 patients (44%; 95% CI, 34-53). The median time to onset of response was 3.3 months (95% CI, 1.7-8.8 months). Treatment-related AEs occurred in 87 (74%) patients with grade 3 or 4 in 20 (17%). The most common AEs included fatigue, asthenia, nausea, and diarrhea. The most common grade 3 or 4 AEs included fatigue, pneumonitis, and diarrhea.⁹⁰

Small Cell Lung Cancer

Small cell lung cancer (SCLC) is a rarer form of lung cancer than NSCLC, responsible for only 10% to 15% of the expected 221,000 new cancer cases in 2015. Lung cancer, including NSCLC and SCLC, is the second most common cancer behind skin cancer.⁶⁵

Pembrolizumab is currently in a phase I, single-arm study (Keynote-28; NCT02054806) for the treatment of SCLC (estimated ennrollment n = 440). This trial was initiated February 2014 with expected completion in April 2016 over which time patients will be treated with 10 kg/mg pembrolizumab every 2 weeks. The primary outcome is best overall response.⁹¹

Nivolumab is also being developed in combination with ipilimumab in SCLC in a phase I/II open-label study (NCT01928394) that was initiated October 2013 with expected completion in December 2017. During this time an expected 1100 patients will be randomized to receive either nivolumab 3 mg/kg every 3 weeks or nivolumab plus ipilimumab (1 + 1 mg/kg, 1 + 3 mg/kg, or 3 + 1 mg/kg every 3 weeks for 4 cycles) followed by nivolumab (3 mg/ kg every 2 weeks).^92,93Interim analysis of 75 patients (nivolumab n = 40; combination n = 35) reveals treatment-related AEs of fatigue (18%), diarrhea (13%), nausea (10%), and decreased appetite (10%) with nivolumab treatment, and fatigue (29%), diarrhea (17%), pruritus (14%), and nausea, endocrine disorders, and rash (11% each) with nivolumab plus ipilimumab treatment. PR was observed in 6 (15%) patients, SD was observed in 9 (22.5%), and PD in 25 (62.5%)patients receiving nivolumab monotherapy. In 20 evaluable patients in the nivolumab plus ipilimumab combination group; there was 1 CR (5%), 4 (20%) PRs, 6 (30%) patients with SD, and 9 (45%) patients with PD. The ORR was 15% versus 25% for nivolumab compared with combination therapy.⁹³

Bladder Cancer

Bladder cancer is a common cancer, and in 2015 there were an estimated 74,000 new cases within the United States accounting for 4.5% of all new cancer cases.⁹⁴It is more common in men, and about 90% of cases occur in individuals over 55 years of age with an average age of 73 years at onset. One-half of cases are diagnosed while the cancer is still in the inner layer of the bladder (noninvasive or in situ), and 35% have cancer that has invaded into the deeper layers but is still nonmetastatic. The overall lifetime risk for development of bladder cancer is 1 in 26 for men and 1 in 90 for women. From SEER data (1988-2001), the 5-year survival rates for bladder cancer based on stage at diagnosis are: 98% for stage 0, 88% stage I, 63% stage II, 46% stage III, and 15% for stage IV.⁹⁵

Bacillus Calmette-Guérin (BCG) has been used as an immunotherapy to treat bladder cancer for 40 years (since 1976) and remains the most effective treatment to date, recommended by the NCCN treatment guidelines as a preferred maintenance and adjuvant treatment, even though it is associated with a list of potential side effects and serious toxicities.^96-98As in other tumor types, PD-L1 expression is associated with a poorer prognosis in metastatic bladder cancer.³³

Checkpoint Inhibitor Use in Bladder Cancer

In June 2014, atezolizumab (PD-L1 inhibitor) was granted extended breakthrough therapy designation by the FDA for the treatment of metastatic urothelial bladder cancer.^32,40,82In a phase I study (NCT01375842), atezolizumab demonstrated clinical benefit, with particularly high response rates in tumors with PD-L1&minus;positive tumor-infiltrating immune cells. Similar to the NSCLC trials, patients (n = 205) were screened and stratified by PD-L1 expression status (using IHC [immunohistochemistry] assay) in tumor cells (TCs) and tumor-infiltrating immune cells (ICs) (TC0, 1, 2, or 3 and IC0, 1, 2, 3).40 The ORR in the groups with an IHC score of 2 or 3 (2/3; indicating either a TC score of 2 or 3 (2/3),or an IC score of 2 or 3 (2/3) indicative of PD-L1&minus;positive tumors; n = 30) was 13 (43.3%; 95% CI, 25.5-62.6), including 2 (7%) CRs compared with the IHC 0/1 group (PD-L1&minus;negative) (n = 35), which displayed an ORR in 4 (11.4%; 95% CI, 4.0-26.3) patients. A total of 68 patients were evaluable for treatment-related AEs with any grade AE reported in 39 (57.4%) and grade 3 or 4 AEs reported in 3 (4.4%) of atezolizumab-treated patients. The most common AEs included decreased appetite, fatigue, nausea, and pyrexia. The most common grade 3 or 4 AEs included asthenia, thrombocytopenia, and blood phosphorus, each present in 1 (1.5%) patient. No irAEs were reported.40 Follow-up with 85 efficacy-available patients (median age 66 years, 75% male) indicated that treatment was well tolerated, and showed durable activity with promising PFS and OS correlating to PD-L1 tumor and blood biomarker status.⁹⁹

Ipilimumab (anti—CTLA-4 therapy) has also been administered preoperatively in the adjuvant setting to six patients with localized urothelial bladder cancer (3 mg/kg prior to radical cystoprostatectomy) demonstrating the feasibility and tolerability of treatment in this setting.¹⁰⁰Further, a positive correlation between CTLA-4 blockade and an increase in the frequency of effector CD4+ T cells that express high levels of ICOS and produce IFN-&gamma; was noted. This was confirmed in a second study of twelve patients (three administered 3 mg/kg and three administered 10 mg/kg) with a primary endpoint of safety and immune monitoring.¹⁰¹In addition, ipilimumab in combination with gemcitabine and cisplatin is also being evaluated as a first-line treatment for urothelial bladder cancer (NCT01524991).

The anti—PD-1 antibody, pembrolizumab, is also being studied in bladder cancer. In the phase III Keynote 045 trial (NCT02256436), patients (n = 470) are to be administered pembrolizumab 200 mg every 3 weeks. This will be compared with investigator&rsquo;s choice of standard of care to determine OS and PFS. This trial is currently ongoing (initiated September 29, 2014) but not recruiting participants.¹⁰²The same dosage of pembrolizumab is being further studied as a first-line therapy in the phase II Keynote 052 study (NCT02335424), in 350 patients with a primary endpoint of ORR.¹⁰³To date, there are no studies of anti—PD-L1 therapies in superficial (nonmetastatic) bladder cancer.⁹⁶