By: Arnold DuBell, Ph.D., M.B.A., Consultant, Clinical & Scientific Assessment, Kantar Health and Stephanie Hawthorne, Ph.D., Vice President, Clinical & Scientific Assessment, Kantar Health
It seems impossible to attend an oncology conference these days without immuno-oncology being a significant focus, and it’s starting to become passé. Well, not quite. Two years ago the idea of this treatment class playing a role in gastrointestinal (GI) cancers seemed unlikely. However, as we learned yesterday at the 2016 American Society of Clinical Oncology (ASCO) Gastrointestinal (GI) Cancers Symposium, these tumors might be immune-sensitive after all. Updated data and new results were reported for several checkpoint inhibitors, which collectively support the continued development of these drugs in GI cancers.
In gastric cancer, first results of the CheckMate-032 trial were presented for Opdivo® (nivolumab, Bristol-Myers Squib/Ono Pharmaceuticals).1 In a heavily pretreated population of 59 patients with gastric or gastroesophageal junction (GEJ) cancer, single-agent Opdivo (at a dose of 3 mg/kg) resulted in a 14% objective response rate (ORR), which included one patient with a complete response. Among the responding patients, median duration of response was 7.1 months. Across all patients, the median progression-free survival (PFS) was 1.4 months, the median overall survival (OS) was 5.0 months, the six-month OS rate was 49%, and encouragingly 36% of patients were alive at one year. There was a slight correlation between ORR and PD-L1 expression, with higher ORR observed in PD-L1-positive patients compared with PD-L1–negative patients (27% versus 12%, using expression in 1% or more of the tumor cells as the definition of PD-L1-positivity). Consistent with studies in other tumor types, Opdivo was well tolerated, with only 17% of patients experiencing a Grade 3 or 4 adverse event. The efficacy data for Opdivo appear, at first glance, to be in line with the activity previously reported for Keytruda® (pembrolizumab, Merck & Co.): 22% ORR, 1.9-month median PFS, and 69% six-month OS in heavily pretreated PD-L1-positive gastric cancer.2
Also debuting data in gastric/GEJ cancer at ASCO GI 2016 was avelumab (MSB0010718C, Merck KGaA/Pfizer). The gastric cancer cohort of the JAVELIN Solid Tumor trial enrolled 75 patients and treated them with avelumab monotherapy in either the second-line setting (n=20) or as maintenance therapy following first-line chemotherapy (n=55).3 In second-line, avelumab produced a 15% ORR and 2.7-month PFS among all patients, and like the Opdivo results there was a suggested correlation between ORR and PD-L1 expression, with higher ORR observed in PD-L1-positive patients compared with PD-L1–negative patients (20% versus 0%, using 1% or more as the definition of PD-L1 positivity along with caution due to small sample sizes). Similar outcomes were reported in the JAVELIN Solid Tumor Japan trial’s gastric cancer cohort: 15% ORR in all patients and suggested correlation with PD-L1 expression (40% in PD-L1-positive versus 7% in PD-L1-negative patients, using 1% or more as the definition of PD-L1 positivity and caution due to small sample sizes).4
Although these study data are all preliminary, they serve collectively to provide evidence that checkpoint inhibition has clinical activity in metastatic gastric cancer and support the multiple Phase III trials that are already underway for all three of these drugs. While these data also suggest PD-L1 overexpression might correlate with improved ORR, the data are reminiscent of outcomes observed in other tumors and further perpetuate ideas that PD-L1 might not be the best biomarker to select patients for treatment with a checkpoint inhibitor.
Results were also reported for this class in metastatic esophageal cancer. The Ono Pharmaceuticals-sponsored Phase II ONO‐4538‐07 study enrolled 65 squamous cell carcinoma esophageal cancer patients and treated them with single-agent Opdivo (3 mg/kg q2w). In this heavily pretreated population, Opdivo produced a 17% ORR by central review, with 1.5-month median PFS and 10.8-month median OS.5 Among those patients who achieved a response, the duration is quite long (median was not reached, but all responding patients seemed to remain in response for at least eight months based on a review of the spider plot). This trial did not provide an analysis of outcomes according to patient PD-L1 status or other biomarker.
The KEYNOTE-028 trial evaluated Keytruda (10 mg/kg q2w) in relapsed/refractory metastatic esophageal cancer patients, specifically enrolling only PD-L1-positive patients, defined as expression in 1% or more of tumor or inflammatory cells or positive bands in the stroma. In patients with predominantly squamous cell carcinoma treated in the third-line or later, the observed ORR of 30% among evaluable patients (n=23) was quite encouraging.6 These efficacy data were a reprisal of data originally presented at ASCO 2015,7 but of particular interest was new data presented on a gene expression signature composed of six genes that play a role in adaptive immune response. In tumors with a high inflamed signature score, there was a propensity toward higher likelihood of prolonged PFS compared with patients with a low score. Even among patients with a high signature score, there still appeared to be a subpopulation with greater benefit, so more work is needed to fully understand how to identify the most responsive patients with PD-1 inhibition, but this data was an intriguing step in the move beyond PD-L1 immunohistochemistry assays.
As in gastric cancer, development of PD-1 inhibitors is advancing quickly in esophageal cancer. Opdivo and Keytruda have recently initiated Phase III trials in this disease, with both targeting the relapsed/refractory setting.
The data for checkpoint inhibitors as reported at ASCO GI 2016 is focused within gastric, GEJ and esophageal cancers. However, previously reported data for Keytruda in colorectal cancer (CRC) was discussed, especially within the context of patient selection for use of checkpoint inhibitors. As reported originally at ASCO 2015, CRC and other GI tumors with high microsatellite instability (MSI-H) or that are deficient in mismatch repair (dMMR) have demonstrated high ORR and prolonged PFS when treated with Keytruda.8 Confirmation of this activity is ongoing in Phase II and Phase III studies. Clinical trials are also currently ongoing with Keytruda and Opdivo in pancreatic cancer and hepatocellular carcinoma. Although we won’t see clinical data in these indications at ASCO GI 2016, today’s Keynote address by Dr. Robert Vonderheide presented intriguing in vitro and in vivo data that supports pursuit of immunotherapy in pancreatic cancer through a combination approach of immune response activation (using chemotherapy, radiotherapy, and/or vaccination) and immune response maintenance (using checkpoint inhibition).9 For now, checkpoint inhibitors continue to garner significant attention across a range of cancer indications, and gastrointestinal cancers can no longer be considered immuno-insensitive.
You must be logged in to post a comment