10 Important Checkpoint Inhibitor Cancer Drug Abstracts from ASCO '15

CHICAGO (The Street) -- For the past few years, the American Society of Clinical Oncology (ASCO) annual meeting has been dominated by cancer immunotherapy -- drugs which activate the body's own immune system to identify and kill cancer cells. In particular, the class of immune-stimulating drugs known as checkpoint inhibitors (also known as PD-1 and PD-L1 inhibitors) has dominated the ASCO spotlight.

This year's ASCO meeting will be no different, except the two leading checkpoint inhibitors -- Merck's (MRK) Keytruda and Bristol-Myers Squibb's (BMY) Opdivo -- have both already secured U.S. approval for skin cancer. Opdivo is also approved in lung cancer and Keytruda is under FDA review for same. There is a lot of clinical work being done to expand the use of checkpoint inhibitors into other forms of cancers, too.

What follows is a quick scan and summary of the ASCO research abstracts released Wednesday night focused on studies of checkpoint inhibitors. In addition to Bristol and Merck, noteworthy data is also being released from Roche (RHHBY), AstraZeneca (AZN) and Pfizer (PFE).

This is not a complete summary of all checkpoint inhibitor data at this year's ASCO meeting, just a taste. And remember, data found in abstracts released Wednesday night are often preliminary, to be updated at the ASCO meeting beginning on May 29.

Merck

Abstract 8011 describes a phase I study (Keynote-021) of Keytruda (pembrolizumab) plus Yervoy in patients with second-line non-small cell lung cancer. Seventeen patients were enrolled and treated with three different dose regimens of Keytruda/Yervoy.

Overall response rate for 11 evaluable patients was 55% (1 complete response, 4 partial responses.) In five evaluable patients treated at the lowest doses, the overall response rate was 60% (3 partial responses.)

Abstract 3009 is a phase I study combining Keytruda and low-dose Yervoy in patients with melanoma and kidney cancer. Responses were observed in both melanoma and kidney cancer patients but the abstract lacks details. Dose-limiting toxicities (all grade 3) were seen in 6 of 19 enrolled patients.

Merck is studying Keytruda in combination with currently approved drugs for newly diagnosed non-small cell lung cancer patients. Abstract 8031 contains preliminary data from the Keynote-021 study, which combines Keytruda with the chemotherapy doublet carboplatin and paclitaxel (Arm A, 20 patients) and Keytruda plus carboplatin, paclitaxel and Alimta (Arm C, 24 patients.)

The preliminary response rate in Arm A was 30%, in Arm C it was 58%. Grade 3-4 adverse event rate was 38% in Arm C. The abstract says additional patients are being enrolled in the Arm C regimen based on "promising" overall response rate.

Abstract 5510 describes a phase I study of Keytruda in patients with PD-L1-positive, advanced ovarian cancer. Twenty-six patients were enrolled. The best overall (confirmed) response to Keytruda was 11.5% (one complete response, two partial responders.) All three patients remained in response for more than 24 weeks at the time of the analysis. Another six patients had stable disease.

Keytruda late-breaker abstracts not released Wednesday night include data in colorectal cancer (abstract LBA100) and head and neck cancer (abstract LBA6008.)

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