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RXi Presents Proof-of-Concept Data for Anti-Scarring, Retinal Programs

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By Bernadette Toner

RXi Pharmaceuticals this week presented initial proof-of-concept in vivo data for its two lead therapeutic programs, showing "robust" uptake of its self-delivering rxRNAs, and successful dose-dependent silencing of target molecules in rodent models.

Speaking at the Rodman & Redshaw Healthcare Conference in New York, RXi President and CEO Noah Beerman provided an update on the company's programs in dermal anti-scarring and retinal disorders, which it initially disclosed in June (GSN 6/17/2010).

In his talk, Beerman reiterated RXI's plan to select a development candidate for the anti-scarring program by the end of the year and to file an investigational new drug application next year. He also said that the company aims to select a development candidate for the retinal program in 2011.

Beerman noted that the potential US market for skin scarring therapies is worth around $4 billion and comprises approximately 42 million surgical procedures per year. In addition, he noted that if the market were to include other anti-scarring indications, such as cosmetic and reconstructive surgeries, burns, and wound healing, it could reach as much as $16 billion in the US.

An anti-scarring treatment based on the firm's sd-rxRNA technology could also have application in other anti-fibrotic indications such as pulmonary and liver fibrosis, acute spinal injury, ocular scarring, and restenosis, he said.

Beerman said that in in vivo proof-of-concept studies, the company's self-delivering rxRNAs have demonstrated "robust" cellular uptake in rats after intradermal injection.

More importantly, he said that in in vivo studies in rat skin, injections of sd-rxRNA knocked down as much as 78 percent of the dermal mRNA target, and that the silencing of the target gene lasts for at least seven days after the last injection.

Regarding RXi's retinal program Beerman estimated that the addressable US market could reach more than $20 billion. Indications include wet and dry age-related macular degeneration, diabetic retinopathy, and diabetic macular edema.

While FDA-approved drugs for wet AMD already exist, such as Genentech's Lucentis and Gilead Sciences' Macugen, Beerman said that the market is "not fully satisfied" with these therapies, and that there is room for a "differentiated product."

In particular, he said that an sd-rxRNA-based drug would provide the opportunity for a "next generation" of retinal disorder treatments because it could extend the time between doses compared to existing therapies.

In proof-of-concept studies with mouse eye models, the sd-rxRNA chemistry demonstrated improved uptake over the company's standard siRNA configuration, which it calls rxRNAori. In a study using fundus camera imaging, the sd-rxRNA molecules demonstrated uptake and localization to the mouse retina after 24 hours. There were no signs of hemorrhage or inflammation, the study also found.

The study also showed the sd-rxRNA molecules can knock down 50 percent of the target mRNA in two mouse models, a level of silencing Beerman called "significant."

In his Rodman & Redshaw talk, Beerman reaffirmed RXi's longer-term pipeline, which is broken down into two areas: "strategic interest," which include projects that the firm can likely take through preclinical development on its own or with strategic partners, and those of "opportunistic pursuit," which include those in which RXi is interested but will backburner pending success of shorter-term goals.

Indications for the former include spinal cord injury and liver cancer, while the latter comprise liver and respiratory diseases, fibrotic conditions, and various cancers.

Beerman did not provide further details about these longer-term projects.

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