On June 1, 2019 Dynavax Technologies Corporation (NASDAQ: DVAX), reported favorable results from the Phase 2 cohort expansion of the Phase 1b/2, open-label, multicenter study of intratumoral SD-101 in combination with KEYTRUDA (pembrolizumab) in anti-PD-1 treatment-naïve patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) (Press release, Dynavax Technologies, JUN 1, 2019, View Source [SID1234536752]). The results were presented today in a poster session at the 2019 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting.

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"We are pleased with the results, particularly when we see a 24% response rate in second-line head and neck squamous cell carcinoma, a tumor that has historically low rates of response to anti-PD-1 treatments," said Robert Janssen, M.D., chief medical officer of Dynavax. "When we look at patients with a combined positive PD-L1 score of less than 20%, their rate of response at 29% was similar to the 25% rate of response for those patients with higher PD-L1 positive scores. Additionally, more than a third of patients with HPV-positive tumors responded. Further, our biomarker data support these clinical outcomes and demonstrate that immunologically cold tumors reach similarly high levels of immune cell infiltration as immunologically hot tumors."

In the Phase 1b/2 clinical study (NCT02521870) in patients with recurrent or metastatic HNSCC, SD-101 is administered intratumorally with 8 mg in 1 lesion or 2 mg in 1–4 lesions combined with intravenous administration of 200 mg of pembrolizumab.

Key highlights from the clinical data presentation include:

An overall response rate (ORR) of 24% (ITT) n = 50 was observed.

An ORR of 22.2% in the 2 mg cohort and an ORR of 26.1% in the 8 mg cohort were observed.
An ORR of 33.3% and a disease control rate (DCR) of 41.6% were observed in patients with low PD-L1 status at baseline.
An ORR of 36% was observed in patients with HPV-positive tumors.
Biomarker data are consistent with the mechanism of action of SD-101 and demonstrate strong immunomodulation of the tumor microenvironment including infiltration of activated T cells and upregulation of Type I and Type II Interferon (IFN).
Importantly, similar to what was reported for melanoma patients who had not received anti-PD-1 therapy (ASCO 2019 Abstract 9534), patients whose tumors exhibited an immunologically cold tumor microenvironment at baseline (low IFNγ and T cell signatures) showed clinical response during SD-101 plus pembrolizumab treatment.
The combination of SD-101 and pembrolizumab was well-tolerated, consistent with previous reports.
No evidence of an increased incidence or severity of adverse events (AEs) over pembrolizumab monotherapy.
No increase in immune-related AEs over pembrolizumab monotherapy.
AEs associated with SD-101 were mainly mild to moderate injection-site reactions and flu-like symptoms that were manageable with over-the-counter medication.
About SD-101
SD-101 is a proprietary, second-generation, Toll-like receptor 9 (TLR9) agonist CpG-C class oligodeoxynucleotide. Dynavax is evaluating SD-101 in several clinical studies to assess its safety and activity, including a Phase 2 study in combination with KEYTRUDA (pembrolizumab) in advanced melanoma and metastatic or recurrent head and neck squamous cell cancer in collaboration with Merck, and in high risk breast cancer in collaboration with I-SPY 2. Dynavax maintains all commercial rights to SD-101.