HTBX: HS-110 Interim Update

By John Vandermosten, CFA


Heat Biologics, Inc. (NASDAQ:HTBX) has continued to progress in their HS-110 Durga trial, recently providing interim results at the ASCO-SITC Clinical Immuno-Oncology Symposium. The Phase II study is evaluating HS-110 in conjunction with checkpoint inhibitors for patients in non-small cell lung cancer (NSCLC) who have failed previous lines of treatment.

The trial uses four cohorts in a study of NSCLC patients that have progressed on previous checkpoint inhibitor therapy and chemotherapy. Results show that HS-110 is well tolerated in combination with nivolumab and that it can stimulate an immune response to tumors and turn “cold” tumors “hot”.

View Exhibit I – HS-110 Trial Design1

Interim data demonstrate tumor shrinkage and disease control in a majority of evaluable patients. For the 38 patients in Cohort A, a partial response was observed in 21%, stable disease in 29%, and disease control in 50% for these patients who have failed previous therapy. Dotted lines bracket RECIST 1.1 criteria between +20% and -30%.

View Exhibit II – Cohort A Objective Response Rate2

Cohort B, which includes patients that have progressed on checkpoint inhibitor therapy, are treated with HS-110 and nivolumab. Results for the group of 18 includes partial response in 20%, stable disease in 35% and disease control in 55%.

View Exhibit III – Cohort B Objective Response Rate

Investigators have observed improved response rates in certain members of the study populations. Patients demonstrating an injection site reaction (ISR) have a statistically significant better survival rate compared to patients without one. The reaction is measured at any one of the administration points and indicates a response to the antigen that is being immunized against. In the small group evaluated, patients with an ISR are 80% more likely to benefit from the therapy.

View Exhibit IV – Survival Comparison Segregated by Injection Site Reaction (ISR)

The investigators have also noted a higher median overall survival (OS) for patients that are above the median in their cytokine secretion as measured by ELISPOT analysis. Patients in the cohort were divided into two groups based on whether they were above or below the median using ELISPOT data. The median survival rate was more than six months greater for the group that was above the median.

View Exhibit V – Median Survival by ELISPOT Analysis Group

Response rates suggest that addition of HS-110 can restore responsiveness to checkpoint inhibitor therapy. Injection site reaction and the expression of cytokines are supportive of the mechanism of action for HS-110 where gp96 presents cancer associated antigens to the immune system, subsequently awakening CD8+ T-cells, which launch an attack against the cancer.

View Exhibit VI – HS-110 Mechanism of Action

The interim data presented in the poster that accompanied the Symposium presentation show HS-110’s ability to work in combination with checkpoint inhibitors to awaken the immune system and help those patients that have already failed on previous therapies. In other words, HS-110 has been able to turn “cold” tumors “hot,” even for patients that have already received checkpoint inhibitor therapy. Based on the RECIST 1.1 criteria, impressive rates of disease control have been demonstrated in both Cohort A and B. Additional observations find that injection site reactions and increased interferon-γ are associated with better overall survival.

The data presented at the ASCO-SITC Symposium demonstrates that HS-110 and nivolumab may restore responsiveness to treatment in NSCLC patients after receiving prior lines of checkpoint inhibitor therapy. We see the data generated so far as supportive of an accelerated path to approval. Upcoming expected milestones for the HS-110 Durga trial include enrollment completion in 2Q:19 and an additional interim readout in 4Q:19.

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1 Source: Heat Biologics Corporate Presentation, February 2019.