BOSTON ( TheStreet) -- Some thoughts, comments and notes in advance of tomorrow's FDA advisory panel meeting to review Vivus' ( VVUS) weight-loss drug Qnexa:

I was asked on Twitter yesterday for my prediction on the outcome of the panel vote on Qnexa. I believe the panel will vote to recommend Qnexa's approval. I'm forecasting a mixed/close vote. This will not be a landslide victory for the drug.

I conducted a quick poll of 20 sources last night -- biotech hedge fund managers, buyside analysts and healthcare brokers -- asking them the same question. The result: 17 votes predicting a positive Qnexa vote, three votes believing the panel will go against the drug.

I'm live blogging Thursday's FDA panel in its entirety. I'll kick things off around 7:45 am EDT, the panel gets underway at 8 am and should wrap up in mid-to-late afternoon. Sign up below if you want an email reminder.

Judging by the rise in the stock prices of Arena Pharmaceuticals ( ARNA) and Orexigen Therapeutics ( OREX), what's good for Vivus might also be good for its obesity drug competitors. That may change depending on the discussion and debate at tomorrow's panel meeting.

Trading in Vivus shares will be halted tomorrow. That leaves traders to play with Arena and Orexigen. It will be interesting to see what level of volatility we get in those stocks as the panel progresses.

I haven't spoken to Vivus in front of tomorrow's panel but the company looks well prepared to tackle the safety concerns and questions that have cropped about Qnexa, judging by the printed agenda. Vivus has five speakers presenting Qnexa data to the advisory panel, including outside experts to discuss neuro-psychiatric safety, pregnancy risks, and risk management plans, including a proposal for a post-approval study to assess cardiovascular outcomes in patients treated with Qnexa.

These safety-related issues are going to be the hot-button topics tomorrow, so Vivus looks ready to make its case. I've covered a lot of FDA advisory panels in my days, and I'm constantly surprised to see how some companies enter this treacherous territory totally unprepared. I don't expect Vivus to fall into that category tomorrow.

I was emailed some commentary from a biotech stock newsletter that's short Vivus. The newsletter said, in part, that the FDA's relatively benign review of Qnexa posted online Tuesday was a bad sign because it gave the agency free reign to carpet bomb the drug with criticism at Thursday's panel.

I disagree. I find that the FDA is never shy about voicing a negative opinion in briefing documents when the agency doesn't like something. What surprised me most about the FDA's Qnexa review was the lack of a smoking gun. I kept waiting for that devastating analysis or piece of negative data that we didn't know about. For the most part, nothing of the sort was in the FDA's review. That's why Vivus shares have been up for the past two days.

I don't anticipate much debate about Qnexa's efficacy. The pill helps obese patients lose weight. Most of the contentious discussion will be about the drug's safety. I'm probably most interested in hearing the discussion on pregnancy risk since this poses a potential problem if/when Qnexa is approved and marketed.

From the FDA's briefing documents, the agency seems very concerned about the number of women in the Qnexa trials who got pregnant despite a requirement that they be using birth control. The two individual components of Qnexa -- phentermine and topiramate -- both carry Category C pregnancy risks, which tells doctors to treat pregnant patients with the drugs if the benefits outweigh the risks.

For Qnexa, however, FDA is recommending a Category X pregnancy warning, which would bar the drug from being used by pregnant women and require Vivus to implement a risk management plan that aims to prevent women of child-bearing age from becoming pregnant while taking Qnexa.

The details of this risk-management plan and how strenuous or arduous it is to implement for doctors and patients represents a significant commercial risk for Qnexa, especially if competing weight-loss drugs are not similarly burdened by a Category X pregnancy warning.

High-dose Qnexa appears to have more problems with side effects and safety than the middle and low doses of the drug. Will this lead FDA or the panel to suggest approving only the middle or low doses of Qnexa? The FDA's review makes no mention of this possible outcome, but the agency's reviewer does question the efficacy of the lowest Qnexa dose. Most of the patients enrolled in the Qnexa phase III studies were treated with the high dose, so does this complicate matters if discussion turns to approving only the middle and/or low doses?

Another wild card tomorrow is the demeanor and stamina of the experts on the advisory panel. Eleven of the 17 voting members Thursday also sat through two days of grueling testimony and debate about the safety of Glaxo's diabetes drug Avandia.

Will all the talk about heart risk tied to Avandia bleed over into the Qnexa discussions? Will the panelists be so grouchy and risk averse that they will vote no for fear that too little is known about the long-term safety of Qnexa?

All these questions will be answered tomorrow. I hope you'll join me for the live blog of the Qnexa panel. I'll have all the play by play and will also answer reader questions and post comments throughout the day.

-- Reported by Adam Feuerstein in Boston.

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