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Genentech Releases Promising Pre-ASCO Data on ALK inhibitor Alectinib, Anti-PD-L1 Immunotherapy

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NEW YORK (GenomeWeb) – Data from an ongoing Phase II study showed that previously treated non-small cell lung cancer patients whose tumors and tumor-infiltrating immune cells expressed the PD-L1 protein at the highest levels lived significantly longer when treated with Roche's anti-PD-L1 immunotherapy compared to those receiving docetaxel.

Although median overall survival hasn't yet been reached for the highest PD-L1 expressers receiving the anti-PD-L1 drug MPDL3280A in the Phase II POPLAR trial, patients whose tumors expressed PD-L1 at lower levels also lived longer on the immunotherapy compared to patients receiving chemotherapy, researchers reported. The drugmaker is using an internally developed immunohistochemistry test in all MPDL3280A studies to prospectively characterize lung cancer patients' PD-L1 expression levels in tumor and immune cells.

Roche subsidiary Genentech announced data from the POPLAR trial ahead of the American Society of Clinical Oncology's annual meeting later this month.

At another medical conference in April, Merck similarly reported that when NSCLC patients had PD-L1 expression in at least half of their tumor cells, their tumors shrank more dramatically and they lived longer on the anti-PD-1 drug Keytruda (pembrolizumab) than those with lower levels of expression. Merck is also using an IHC assay to identify PD-L1 expressers in clinical trials and has set specific cut-offs for determining high, intermediate, and low PD-L1 groups.

However, unlike Roche/Genentech's assessment of PD-L1 expression on both tumor and tumor- infiltrating immune cells in POPLAR, Merck is tracking expression only on tumor cells. A Genentech spokesperson explained to GenomeWeb that a patient had to have IHC staining for PD-L1 in 1 percent or more tumor cells (TC) or tumor-infiltrating immune cells (IC) to be deemed a low (TC1/IC1), medium (TC2/IC2), and high (TC3/IC3) expresser.

Recognizing there are multiple drugmakers developing anti-PD-L1 and -PD-1 treatments with different companion diagnostics that may define PD-L1 expression in different ways, the US Food and Drug Administration is working with industry to explore testing differences and develop standards. The agency held a meeting recently on this topic.

"Large, ongoing clinical studies are examining the significance of measuring the amount of PD-L1 on tumor cells and tumor-infiltrating immune cells and how expression correlates with outcomes for patients in multiple types of cancer," the Genentech spokesperson said. "It's important to note that the level of PD-L1 overexpression that correlates with use of PD-L1 as a biomarker for treatment decisions may be different for each disease and requires validation in each type of cancer."

After the results from a second Phase II trial, BIRCH, are reported later this year, Genentech is hoping to make a submission for MPDL3280A with the FDA in lung cancer next year. Additionally, Genentech said it is planning to file a new drug application this year for another NSCLC drug, alectinib, based on early-phase data showing that the agent shrank tumors in patients previously treated with Pfizer's Xalkori and those with brain metastases.

MPDL3280A

The level of PD-L1 expression correlated with a survival advantage in this first randomized trial for MPDL3280A involving nearly 300 patients, according to Sandra Horning, Roche's chief medical officer. "The goal of PD-L1 as a biomarker is to identify people most likely to experience improved overall survival with MPDL3280A alone and which people may be appropriate candidates for a combination of medicines," she noted. Experts have said that low-expressing PD-L1 patients may be good candidates for studies investigating immunotherapies in combination with drugs that boost the body's ability to attack cancer cells.

When PD-L1 receptors on tumor cells and PD-1 receptors on T cells come together, it jams up the immune system's ability to recognize tumor cells. MPDL3280A blocks PD-L1 receptors on tumor and tumor-infiltrating immune cells from interacting with PD-1 receptors on cancer-killing T cells, which enables T cells to once again recognize cancer cells and attack them.

Using the IHC test, researchers in POPLAR determined the PD-L1 expression level for patients and gave them a score between 0 (no expression) and 3 (high expression) for tumor and tumor-infiltrating immune cells. In the MPDL3280A-treated arm, patients with a score of 3 hadn't reached median overall survival, but for those on docetaxel, median overall survival was 11.1 months. In those with scores of 2 or 3, the median overall survival was 13 months in the MPDL3280A arm compared to 7.4 months in the docetaxel arm.

Median overall survival had also not been reached when patients with scores of 1, 2, or 3, were combined, but was 9.1 months for those receiving docetaxel. In patients with a score of 0, median overall survival was 9.7 in both arms.

Median progression-free survival was the longest at 9.7 months for those treated with MPDL3280A and scores of 3, and declined among lower PD-L1 expressing groups. The median progression-free survival remained between three and four months in the docetaxel arm across PD-L1 expressing groups. The overall response rate on MPDL3280A was also best for patients with the highest PD-L1 expression.

These data suggest that the higher the level of PD-L1 expression is for NSCLC patients, the better the chances that they will live longer with MPDL3280A treatment. And even when patients have lower levels of PD-L1 expression they stand to derive a benefit from MPDL3280A compared to docetaxel.

Patients receiving Roche's anti-PD-L1 drug had more respiratory events, but Grade 3 to 5 toxicities were lower compared to those on docetaxel, and patients in the MPDL3280A arm continued with the treatment longer than those receiving chemo. Patients receiving MPDL3280A experienced immune-related toxicities such as increased blood enzymes, and inflamed colon, liver, and lung tissues.

MPDL3280A has breakthrough therapy designation from the FDA. In addition to POPLAR, Roche is studying MPDL3280A in three Phase II and six Phase III trials in various types of lung tumors.

Alectinib

Roche also announced ahead of the ASCO annual meeting results from two studies showing that the NSCLC drug alectinib shrank tumors in around 50 percent of patients with advanced, ALK-positive tumors who had progressed after treatment with Xalkori. In these two studies (dubbed NP28673and NP28761), patients experienced median duration of response of 11.2 and 7.5 months, respectively.

In the nearly 140-patient single-arm trial, NP28673, the median progression-free survival was 8.9 months for those on alectinib after becoming refractory to Xalkori. In the 87-patient NP28761 study, median progression-free survival was 6.3 months, but according to Roche this data has not yet matured.

Promisingly, in patients whose cancer had spread to the central nervous system, alectinib also shrank tumors in 57 percent of patients in the NP28673 study and 69 percent of those in NP28761. About half of those with ALK-positive lung cancer experience brain metastases. The blood-brain barrier mechanisms that hold molecules at bay from affecting the brain don't recognize alectinib, allowing the drug to enter brain tissue, according to Roche.

Common adverse events in these trials included increases in muscle enzymes and liver enzymes, and shortness of breath.

The FDA granted breakthrough therapy designation for alectinib in 2013 as a treatment for ALK-positive NSCLC population who are non-responsive to Xalkori. Developed by Chugai Kamakura Research Laboratories, alectinib became available for patients in Japan last September and is being marketed there by Chugai Pharmaceutical, a Roche subsidiary.

In studies where patients have previously received the ALK inhibitor Xalkori, a companion test is likely unnecessary since patients will already have been tested for ALK rearrangements. Still, in studies where Roche is exploring the use of alectinib in earlier NSCLC settings, the company said it is identifying ALK-positive patients with an internally developed companion diagnostic. Specifically, the ALEX Phase III trial comparing alectinib against Xalkori as a first-line treatment for advanced NSCLC patients with ALK rearrangements involves the use of a companion IHC test.

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