Adventrx's Exelbine Could Be Available This Year

| About: Mast Therapeutics, (MSTX)

With company’s Sept. 1 PDUFA date for Exelbine (ANX-530) for non-small-cell lung cancer only two months away, I had the fortunate opportunity to speak with the CEO of the company, Brian Culley, last week. The notable items from the interview are below as well as additional information about the company.

Culley said that the company expects to have the product in the market this year if it is approved on Sept. 1 and the company will provide more guidance after approval. Culley said that it will take roughly three to four years to ramp up sales to a steady state, but that depends on many factors. He noted that the company has to balance reaching the market as much as possible with commercial planning and the right level of promotional activity. Adventrx plans to use approximately 12 field reps for ANX-530.

Because ANX-530 is not a new drug, but just a new dosage form of a current drug on the market, physicians know how to use it. Therefore, there is no need to teach physicians about the drug. The training process will be a lot simpler and require less time and education. He added that the commercial reach of a rep will be quite large.

The company expects to price 10mg of Exelbine at between $50-100. The company does not expect to gain 100% of the market, but enough of it so that its share will be extremely beneficial.

ANX-188 is a very compelling product candidate. It has been tested in patients and had strong signs of efficacy. There is a lot of evidence the drug works and there is a forgiving competitive landscape. There is a 100k patient market and it has been designated an orphan drug. Culley also noted that ANX-188 is the product candidate furthest along in the sickle cell space. The company expects to start the Phase 3 clinical 3 trial in 1H12, but is not sure how long enrollment will take. There was a different company that had 255 patients in its trial, and it took around 18 months to get them enrolled in the study. Adventrx’s study will have approximately that many patients as well.

Company Background

Including ANX-530, the company has three late-stage programs: Two in oncology that are reformulations of current FDA-approved drugs, and one in hematology that is a new product candidate. The company’s most advanced product candidate is ANX-530.

ANX-530 is the company’s proprietary emulsion formulation of vinorelbine. Vinorelbine is a vesicant and venous irritant, and these adverse effects can limit its tolerability. ANX-530 was designed to be bioequivalent to the reference drug while reducing the incidence and severity of vein irritation associated with intravenous delivery of the drug. In a clinical bioequivalence study, ANX-530 and the reference drug were determined to be bioequivalent. The NDA was accepted for filing on Jan. 6 and later in January assigned a PDUFA date of Sept. 1.

The company has two other late-stage products that it is focusing on developing. The first, ANX-188 (poloxamer 188) for sickle cell disease, was acquired as part of the company’s acquisition of SynthRx this year. Research has demonstrated that poloxamer 188 adheres to hydrophobic surfaces that develop when cells are damaged and restores normal hydrated surfaces, while having little or no activity in normal, healthy tissues. Adventrx is currently planning to meet with the FDA to reach agreement on a phase 3 clinical trial protocol for ANX-188.

In 2001, the results of the phase 3 study that tested ANX-188 for sickle cell disease were published in the Journal of the American Medical Association. The conclusion of the study was that a decrease in the duration of painful episodes and an increase in the proportion of patients who achieved resolution of the symptoms were observed when the purified poloxamer 188-treated patients were compared with the patients receiving placebo. However, the difference between these groups was significant but relatively small. In subgroup analysis, a more significant effect on both parameters was observed in children and in patients who were receiving concomitant hydroxyurea.

Further, the authors of the study noted that it is important to emphasize that in an earlier phase 2 study, even greater benefits with the product candidate had been observed. This disparity may be explained at least in part by the assumptions used in its definition of crisis duration, the primary end point in this study. It was further noted that in the Phase 3 study, the company used an extremely stringent definition of crisis resolution that represented a very conservative approach to the analysis of the data.

The other product candidate is ANX-514 -- a novel emulsion formulation of the chemotherapy drug docetaxel, a formulation of which is marketed under the brand name Taxotere. It is formulated without polysorbate 80 or other detergents and is being developed to reduce the incidence and severity of side effects associated with detergents, such as hypersensitivity reactions. Adventrx met with the FDA in February 2011. The FDA indicated that a randomized safety study comparing ANX-514 and Taxotere would be required in an appropriate patient population to support approval of ANX-514. The study would be primarily descriptive but with a sample size sufficient to demonstrate a comparable safety profile. The FDA recommended that the study also collect data on response rate and duration of response. The company currently is developing a study protocol for submission to the FDA and intends to continue discussions with the FDA regarding the phase 3 study and other requirements for approval of ANX-514.

The financials are in decent shape. The company had over $46 million in cash at the end of last quarter. The cash position received a boost earlier this year after Adventrx raised $22.5 million. The company has no revenues and reported a loss of $3.0 million in Q1.

Disclosure: I have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours.