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Sarepta Therapeutics, Inc. Message Board

  • bionerd51 bionerd51 Aug 15, 2013 10:24 AM Flag

    Phase II Data and Protein Assay's...

    Immunoflorescence is more sensitive for protein quantification. I would have done both [Western blot]. This phaseII trial was designed as a proof-of-concept study. One thing this hack says is that Sarepta should have done total dystrophin vs. + fibers but as long as there is a baseline + dystrophin fibers count comparative analysis can be done. From a functional standpoint the + fiber count is more important so both measurements are useful. Getting back to the proof-of-concept design, the FDA's request for additional quantification of dystrophin and dystrophin as a surrogate marker info is standard especially considering the trial design and small population. In context this is a prudent request. If this request was based on PhaseIII data and NDA filing that might raise a red flag. The surrogate marker request is the FDA's job when assessing a particular surrogate marker for the first time. This blogger [anyone can blog] if my memory serves me was a big Genta investor and Genasense believer. genasense was one of the biggest antisense failures of all time. The only hint of efficacy in the Genasense phaseII data was via an immune response, similar to vitravene. In the last couple of years he has switched from phosphorothioate AO's to RNAi. A chemistry which is in it's infancy in drug development. By the way and whether through Western Blot or immunoflorescence assay has Glaxo released their dystrophin numbers yet?? What does Dirk have to say about that?

    Sentiment: Strong Buy

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    • Thanks, Nerd.

      Sentiment: Strong Buy

    • I guess i was right about the Drisa dystrophin data. Now Glaxo should release the dystrophin breakdown [pt. by pt.]. I don't expect it.

      Sentiment: Strong Buy

    • I really appreciate your knowledge, bionerd, although I feel I need a glossary to keep up.

    • Bionerd, I believe the "Dirk" of the infamous Genta saga was Dirk Raat. Br'er

    • Genasense was for cancer and WAS a TOTAL FAILURE, to the extent that the company (Genta)went bankrupt and faded into history/dust!

      Sentiment: Buy

    • Got called away.. One more thing regarding total dystrophin vs. dystrophin + fibers debate is in the DMD muscle pathology decreased dystrophin turns into fibrotic tissue. It is common to have a high total dystrophin count in a small section of a myocyte. As a result you can have a 30% total dystrophin count but + fibers is 10%. I think if one looks at the orginal Drisa proof-of-concept study conducted by Prosensa, that had no placebo cohort, they reported elevated + fibers but never released a corresponding baseline number. This is a common technique that small biotechs use to manipulate efficacy #'s in an effort to garner a much needed cash infusion via a big pharma deal.

      Sentiment: Strong Buy

      • 3 Replies to bionerd51
      • Very key concept, "Nerd. If one gets lucky and hit a single functional muscle cell with lots of dystrophin is will make total dystrophin look high even though the muscle cell you happened to sample was the only one remaining. If you survey the whole population of muscle cells and note the percentage with dysrophin then the result won't be skewed.

      • Anyway you chop it up ,producing ''dystrophin'' creates a series of events that changes the disease outcome of these dmd boys...we all including the fda can have opinions how to come up with the right solution of why this drug is working but that facts are ..the drug is working wonderfully .

      • One last comment on Dirk H.,the blogger, I have tried several times to engage this guy in an internet discussion on antisense chemistry and he refuses to directly respond to any of my rebuttals. He is a PMO naysayer because of Stanley Crooke, CEO of Isis. He has been knocking the PMO for decades. Crooke reports that the PMO does not regularly enters cells and he cites the individual cell uptake test that all researchers use when testing cellular uptake of AO's. Since the PMO is nonionic in physiological pH the phosphorothioates gain entry more readily in this test environment because the S=DNA's are highly charged molecules. Through charge/charge interactions the 2'MOE enters at a higher rate than the PMO. This is true but when you use a multicellular host in the experiment the PMO enters more readily. use a nonhuman primate or human the PMO enters more readily than the 2'OME/MOE and that is because these highly charged molecules get hung up on proteins throughout the system inhibiting cellular uptake. I have been trying for years for Dirk to answer the following query... If the PMO does not readily enter cells how do you explain the uptake of epithelial cells and antiviral effect in nonhuman primates to the tune of a 7LOG10 reduction in Marburg virus? He has no answer. There are no papers that document an immune reaction as the cause of any antiviral effect. Years ago the S=DNA's were used in antiviral studies and they BOMBED. Which compound has cell uptake challenges, the PMO or the S=DNA's????

        Sentiment: Strong Buy

    • Yeah!..... What he say!
      GO GET ' EM NERD

    • The phase 1 study used both assays. My recollection is that this study established the validity of the fiber count measurement. So it is disingenuous to attack the assay out of context.

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