@bracketanalytix retorted with, "I get it. I don't expect you to ever change on $NAVB -- regardless of facts. Nothing changed in 6 mos?"

To which I tweeted: "When facts change, investment thesis should change too. With $NAVB and Lymphoseek, facts haven't changed. Understand?"

To elaborate, the bear thesis on Navidea assumed Lymphoseek approval. FDA actually approving Lymphoseek on Wednesday was positive for Navidea, for sure, but it wasn't a surprise and doesn't change my thinking on the stock since I always assumed the product would reach the market. I will gladly change my view of Navidea if Lymphoseek is more successful than I predict, and I will admit being wrong. Nothing I've seen so far makes me want to change my mind.

@jasonMilano8 asks, "Is $AFFY a good buy here for a spec play? Or long-term hold?"

Affymax ( AFFY) is up about 25% since I wrote: Affymax is Done. RIP But at $3 and change, Affymax shares are still down 80% since the anemia drug Omontys was pulled out of dialysis clinics in late February after reports surfaced of severe allergic reactions and deaths.

If you owned Affymax in February, you're still in a deep hole. If you bought it after the stock crashed, you're a lot happier.

Omontys is a dead product unless Affymax and partner Takeda can figure out the cause of the problem. And even if a cause is found and corrected, getting the drug back into dialysis clinics and used will be a real challenge. Is the price savings afforded by Omontys over other anemia drugs worth the safety risk? I stand by my Affymax headline until we get more information about Omontys.

Until then, we've certainly seen Affymax shares whipsawed by trading rumors, most of them false. Does that make the stock a good spec trade? I'll let traders decide on their own. My perspective is more fundamental, which means Affymax has a long way to go before getting back to $16.

Worth reading: David Sobek's provocatively titled Sangamo BioScience: The Impending Failure in HIV. Sobek is a Sangamo ( SGMO) bull who believes, like I wrote last week, that the company is wasting time and money on SB-728.

Sobek:

Given the lofty expectations and concurrent run up in shares, it appears that expectations have gone too far. SGMO shares have more than doubled in the past several months and trade over $9 (roughly a $500 million market capitalization company). The key to Sangamo's long-term value, however, is its monogenic disease platform, but this is still pre-clinical. While the idea of a functional cure is exciting, the odds of success are very low. The most likely scenario is that the phase II trials will not meet the raised expectations and cause a revaluation of the company.

Coincidentally, I had a conversation with an institutional investor this week who's been buying Sangamo for the potential of its preclinical pipeline but is hesitant to add to his position until the HIV program is back-burnered. If the SB-278 phase II data disappoint and Sangamo shares fall, you might see significant weakness bought.

Ziopharm Oncology ( ZIOP) update: Following "close dialogue" with the FDA, palifosfamide will now be considered for full approval as a treatment for sarcoma based on a progression-free survival benefit, a company spokesperson told me. Previously, PFS was only being considered as the basis for accelerated approval with overall survival required for full approval.

The change is positive news for Ziopharm and should alleviate some of the regulatory concerns that have weighed on the stock as we get closer to the data read-out from the palifosfamide study during the last week of March.

TG Therapeutics ( TGTX) CEO Michael Weiss was unhappy with the way I characterized his track record with Keryx Pharmaceuticals ( KERX) and as a lieutenant of health-care investor Lindsay Rosenwald. Many Wall Street investors look askance at companies with a Rosenwald-Weiss provenance. Weiss says he deserves a fairer shake:

With your piece on TG Therapeutics, you had an opportunity to set the record straight on my track record and use that as a positive reason for investors to look at TG Therapeutics. Unfortunately, you chose to continue to misrepresent me. Looking objectively with 20/20 hindsight, it's hard to dispute our success at Keryx. When I took over Keryx in December 2002, the company was in disarray and had zero enterprise value. I spent seven-plus years re-building and re-creating Keryx. I built a terrific team, a number of whom are with me now at TG Therapeutics, and together we built a strong product pipeline designed to make Keryx a company that had multiple opportunities to succeed. We inherited sulodexide, we later acquired ACCESS Oncology (a company I founded in 1999) with their lead product, perifosine, and we in-licensed Zerenex, which now has two positive phase 3 studies. With a .333 batting average, our record matches up to some of the most successful teams in biotech.

I'd also like to say we got smarter over the years, and at TG we are applying what we learned, both positive and negative. We are very excited about TG-1101, an anti-CD20 monoclonal antibody with a market opportunity projected to exceed $10 billion. The clinical program for TG-1101 is under way. Similar to my approach at Keryx, my goal at TG is to build a company with multiple opportunities to succeed. To that end, we added TGR-1202, our novel PI3K delta inhibitor, to our development pipeline this summer. Our PI3K delta, as you correctly point out, is early in development. We know we have the right target, but do we have the right drug? Today that answer is unknowable. Stay tuned as we hopefully will know a lot more over the course of the year.

-- Reported by Adam Feuerstein in Boston.

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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