These patients -- among the most difficult breast cancer patients to treat -- reported the biggest benefit in the phase II study reported last December. Treatment with CDX-011 led to a 33% response rate compared to no responses in patients treated with "investigator's choice" chemotherapy. CDX-011 doubled the time before tumors started to grow again to a median of three months compared to 1.5 months for control-arm patients. Median overall survival almost doubled in the CDX-011-treated patients to a median 10 months versus 5.5 months for patients in the control arm.

Great results but the data were derived from just 12 patients treated with CDX-011 and four patients in the control arm. The biggest forward risk in the Celldex CDX-011 is that this efficacy signal from the phase II study is a false positive that will prove negative once the pivotal study is run. Don't underestimate this risk, even if you're a Celldex fan.

Celldex reports 2012 financial results in March, which is when I expect the company will offer more details about the CDX-011 pivotal trial. For now, consider the FDA's agreement to allow an accelerated approval study to be a positive development for the company.

BuggyFunBunny writes, "And what of nucs now that Idenix Pharmaceuticals (IDIX) abandons. Is the entire family done for?"

Not all nucleoside/nucleotide polymerase inhibitors -- "nucs" -- in hepatitis C are the same. The chemical structure of these drugs matter. Guanosine-based nucs are bad.

Bristol-Myers Squibb's ( BMY) BMS-096084 was a guanosine nuc and it caused severe cardiac toxicity, killing one patient in a clinical trial. Idenix didn't find cardiac toxicity with its guanosine nucs IDX184 and IDX19368, but FDA decided, smartly, that the safety risk of any guanosine-based nuc is too great.

Gilead Sciences' ( GILD) blockbuster-in-the-making, sofosbuvir, is a uridine-based nuc, so is Vertex Pharmaceuticals' ( VRTX) VX-135. Idenix also has a uridine nuc in preclinical development, expected to begin human studies this year.

Here's the simple rule: Uridine nuc good; guanosine nuc bad. Of course, not all uridine nucs are equally good, but that's a discussion for another day.

On a related note, @VendettaUhave asks, "$MDGN if the goal is to eliminate interferon therapy, is it pointless to invest here? Any upside in this name?"

This is Medgenics ( MDGN): Doctors take some dermal tissue from just under the skin of the arm. This tissue sample is then placed inside a black box where the cells of the sample are genetically altered and programmed to produce a therapeutic protein (a drug) of your choice. The tissue sample -- now called a "biopump" -- is implanted back into the patient where it merrily produces drug. Multiple biopumps will be necessary.

Really? Let's be overly generous and assume these Medgenics biopumps are actually capable of producing drugs at therapeutic levels. How do the biopumps know how much drug to deliver? How are appropriate blood levels of the drug maintained without a feedback loop or any way to turn them on or off? Do the biopumps work forever or do they wear out? What happens when they wear out? Are they removed? Do they need to be replaced?

Medgenics is developing a biopump to produce the anemia-boosting drug EPO. Does this process really sound better or more convenient than simply giving a patient an injection of EPO when needed? The answer: no.

The company is also developing a biopump to produce interferon as a treatment for hepatitis C. Well, by next year, hepatitis C patients won't require interferon. The next generation of potent direct antivirals coming soon from Gilead and others will make interferon injections obsolete. Hepatitis C patients will take a pill or two for 12 weeks and their hepatitis C infection will be cured.

Isn't that a lot easier than having biopumps installed under your skin? Again, the answer is yes.

Sol Barer, the former CEO of Celgene, is the chairman of Medgenics. Which prompts me to ask: "Sol, what the hell are you thinking?"

-- 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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