When the U.S. Food and Drug Administration cancels previously scheduled advisory panel meetings, the agency's most frequent next decision is the rejection of the drug under review.

This FDA pattern, seen over the past 10 years, could spell trouble for Dynavax Technologies (DVAX) , which is seeking U.S. marketing approval for an experimental hepatitis B vaccine known as Heplisav.

The FDA scheduled an advisory panel for November to review Heplisav. Then the FDA cancelled the panel. Investors have been left to guess what happens in December when the agency is expected to decide if the hepatitis B vaccine should be approved or rejected.

The FDA's regulatory precedents don't not always repeat, but if they do Dynavax should be worried.

When I wrote about Dynavax and the controversial Heplisav FDA review in last week's Biotech Stock Mailbag, I suggested a homework assignment:

... someone could look back to find all the instances where FDA cancelled previously scheduled advisory panel meetings, then check to see if the drug involved was approved or rejected. That might give you some additional insight into what will happen to Dynavax.

Sure enough, an investor source of mine did the work. He shared his results with me, and I'm sharing them with you.

This investor looked as far back as 2008-2009 and found 15 instances where the FDA cancelled a previously scheduled advisory panel meeting. In 13 of those 15 examples, the FDA later rejected the drug on that review cycle.

The two exceptions where FDA approved drugs even with cancelled advisory panel meetings were Yervoy, the melanoma drug from Bristol-Myers Squibb  (BMY) , a holding in Jim Cramer's Action Alerts PLUS portfolio, and Pomalyst, Celgene's  (CELG) multiple myeloma drug.

This is how the FDA worded the announcement of the Pomalyst advisory panel cancellation:

The issues for which the FDA was seeking the scientific input of the committee have been resolved.

And this how the FDA worded the announcement of the Yervoy advisory panel cancellation:

The February 9, 2011, ODAC meeting has been cancelled because the issues for which the FDA was seeking the scientific input of the committee have been resolved.

In both examples, the FDA signaled the drugs' eventual approval.

The language used by FDA in its notice cancelling the Dynavax Heplisav advisory panel was different. Here it is:

The November 16, 2016 Vaccines and Related Biological Products Advisory Committee [VRBPAC] meeting, to discuss and make recommendations on the safety and efficacy of a Hepatitis B Vaccine manufactured by Dynavax, has been cancelled to allow time for the FDA to review and resolve several outstanding issues. The agency intends to continue evaluating and will schedule an Advisory Committee meeting in the future, as needed.

In his research, my investor source found this same language used by FDA in 2009 when it cancelled an advisory panel for an iron chelating drug known as Ferriprox.

The October 6, 2009, ODAC meeting has been cancelled to allow time for the FDA to review and resolve several outstanding issues. The Agency intends to continue evaluating NDA 021-825 and, as needed, may schedule an Advisory Committee meeting in the future.

The FDA used the exact same language in 2009 to explain the cancellation of the Ferriprox advisory panel as it just did to cancel the Dynavax Heplisav meeting.

In November 2009, FDA rejected Ferriprox.

To be absolutely clear, none of this guarantees an FDA rejection of Heplisav on or before the Dec. 15 decision date. Every drug review is different and Dynavax may have answered the FDA's outstanding questions sufficiently to allow for the vaccine's approval.

On Monday, Dynavax filed an 8-K with the Securities and Exchange Commission stating it had "received anticipated requests for information from the U.S. Food and Drug Administration's review team in connection with the pending Biologics License Application ("BLA") for HEPLISAV-B. The review team's questions are in line with the company's expectations."

The company's statement implies the Heplisav review is going well despite the cancelled advisory panel meeting.

J.P. Morgan analyst Anupam Rama interpreted Dynavax's statement as "reflecting increased likelihood that the December PDUFA date is met (which we agree with in that ultimately we believe Heplisav will be approved; our model has 75% probability of success)."

But again, the history of FDA advisory panel cancellations suggests drug rejections, not approvals, are more likely.

The compliance rules of the hedge fund where my investor source work restricts him from being identified by name. However, he's confident enough in his research to take a short position in Dynavax heading into the Dec. 14 FDA decision date for Heplisav. Full disclosure.

Independently, a second buy-side biotech analyst appears to have done similar research and reached the same conclusion about Dynavax. This analyst, who goes by the Twitter handle @zbiotech, tweeted Tuesday:

over past 10yrs, 10/13 FDA panels that were cancelled/not resched led to CRLs for 1st time NDA/BLAs...approvals were cancer drugs $DVAX

— zach (@zbiotech) October 4, 2016

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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