Vical Herpes Vaccine Clinical Trial Disappoints with "Confounding Results"
June 23, 2015
By Mark Terry, BioSpace.com Breaking News Staff
The NASDAQ temporarily halted sale of San Diego-based Vical stock yesterday in anticipation of news regarding its Phase I/II clinical trial for a genital herpes vaccine. Unfortunately, the trial did not meet either of its primary endpoints and trading resumed with a major drop in share prices.
The trial was conducted across seven sites in the U.S. and had two goals, to test a monovalent (gD) vaccine and a bivalent (gD + UL46) vaccine utilizing Vical’s proprietary Vaxfectin adjuvant. An adjuvant is a molecule added to a drug or therapy or vaccine that is designed to enhance the body’s immune response.
The study’s primary endpoint was a change in viral shedding rate and genital herpes lesions in herpes simplex virus type 2 (HSV-2) patients. Neither of the study’s primary endpoints were met.
“We just received the top-line study data and we are disappointed that the vaccines did not meet the primary endpoint,” said Vijay Samant, president and chief executive officer of Vical in a statement.
“The trial is ongoing and all patients are being followed for safety for 12 months and efficacy for nine months after their final vaccine dose. During that nine-month period, we will collect additional clinical efficacy data including recurrence rate and lesion rate, which will enable us to determine the appropriate next steps for this program. We greatly appreciate the ongoing support of the patients and investigators who are taking part in this trial.”
Not surprisingly, Vical stock took a hit. Prior to the news, shares traded for $1.42 per share. After the news, shares sold for $0.73. Only recently had the shares been selling that high. For the last year stock was trading somewhat unevenly, but on a slightly downward trend.
Shares traded for $1.30 on July 29, 2014, dropped to $1.00 on Jan. 7, 2015, rose to $1.17 on Jan. 14, 2015, dropped again to $0.85 on Mar. 26, 2015 and traded for $0.98 on June 6, 2015.
The company is not new to failed vaccine trials. On Aug. 12, 2013, Vical announced top-line results from a Phase III trial of Allovectin, an intratumoral cancer immunotherapy in patients with metastatic melanoma. In that 390-patient trial, primary endpoints were not met in a study that examined the vaccine’s effectiveness compared to first-line chemotherapy. It failed, as well, to meet secondary efficacy endpoints. As a result, the company shifted its focus to infectious disease vaccines.
In response to its failed herpes vaccine trial, the company indicated it would continue its focus on its CMV (cytomegalovirus) vaccine candidate in partnership with Astrellas.
“Enrollment is complete in the Phase II solid organ transplant trial, placing us on track for data during the second half of 2016, and the Phase III pivotal trial is underway in hematopoietic stem cell transplant recipients,” said Samant in a statement. “We are also moving our in-licensed antifungal compound toward a Phase I trial initiation during the first half of 2016. Because Astellas funds the CMV program and given the other operational efficiencies we have put in place, we anticipate that our current cash flow position will fund us through these milestones and into 2017.”
Further complicating the herpes study was the unexpected evidence of greater viral shedding in the placebo group, evidence that the company admits they don’t yet understand.
“The placebo group offered confounding results,” said Astrellas Mammen “Anza” Mammen, vice president of Vical clinical vaccines in yesterday’s conference call “The placebo used in this trial is a phosphate buffered saline, PBS, which should not have any biological activity. This group was primarily included as a safety comparison and therefore was designed to be small, with just 21 patients. The study was not designed to compare the placebo and vaccine arm. But the fact is, the placebo group had a higher shedding rate of 18.4 percen compared to less than 15 percent in each of the vaccine arms.”
Further analysis as more data comes in will be necessary.
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So BioSpace wants to ask our readers again what they predict for this new dealmaking bonanza. Will Glaxo go—and if so, to whom?