April 9, 2011

More on Histone Deacetylase Inhibitor

University of Notre Dame Press Release Claims Breakthrough

A paper claiming a breakthrough in the fight against Niemann-Pick Disease Type C (NPC) appeared in a recent issue of Proceedings of the National Academy of Sciences (PNAS). The paper, coauthored by Olaf Wiest and Paul Helquist of the University of Notre Dame and Frederick Maxfield of Cornell University, says the use of an unspecified histone deacetylase inhibitor corrects the damage done by the genetic disorder NPC and allowed once-diseased cells to function normally. Follow this link to view an abstract of this paper at PNAS: http://www.pnas.org/content/early/2011/03/15/1014890108

To help understand the press release issued by Notre Dame on March 21, the NNPDF consulted three respected experts in Niemann-Pick Disease Type C: Dr. Dan Ory of Washington University, Dr. Marc Patterson of Mayo Clinic, and Dr. Denny Porter of the National Institutes of Health. Follow this link to view the Notre Dame press release dated March 21, 2011: http://www.eurekalert.org/pub_releases/2011-03/uond-bin032111.php

Daniel Ory, M.D., Washington University School of Medicine, and Chair of the NNPDF’s Scientific Advisory Board, responded to our inquiry:

The results are promising, but represent an early step in the process of identifying effective compounds for NPC. More cell studies are needed to understand the mechanism [and] mouse studies should be pursued….there is a long history of compounds that are effective in reducing cholesterol in cultured cells but do not have benefits in animal models, so we should be cautious in extrapolating such results to humans.

Marc C. Patterson, M.D., Chair of the Division of Child and Adolescent Neurology at Mayo Clinic, also a member of the NNPDF’s SAB, further cautioned against making premature assumptions:

The work was done in cultured fibroblasts, so one should be very cautious about extrapolating these data to animals or humans. Moreover, the work was done in cells expressing one or two I1061T NPC1 mutations, and may not be relevant to other mutations; it was not effective in an NPC2 mutant cell line. Of note, the late Dick Pagano showed dramatic reversal of trafficking abnormalities and filipin staining in NPC fibroblasts in which rab 7 and 9 were overexpressed, but much more modest results in transgenic mice with NPC1 mutations and rab overexpression.

Mouse studies could certainly be justified, but it would be premature to assume that this approach will be applicable in humans with NPC.

Another of the NNPDF's SAB members, Forbes “Denny” Porter, M.D., Ph.D., of the National Institute of Child Health and Human Development at the National Institutes of Health (NIH), stated, “It is always good news to have a potential new approach to treating NPC. Cells are the starting point, but to translate this to a potential therapy more work needs to be done.”

The paper by Wiest, Helquist and Maxfield does not name the specific histone deacetylase inhibitor. Histone deacetylase inhibitors (referred to as HDAC inhibitors) are a class of compounds that interfere with the function of histone deactylase. HDAC inhibitors have a history of use in psychiatry and neurology as mood stabilizers and anti-epileptics.

One HDAC inhibitor, valproic acid, was considered as a possible treatment for NPC, but results have not been overly promising.

Yiannis Ioannou, Ph.D., Department of Genetics and Genomic Sciences at Mount Sinai School of Medicine, also a member of the NNPDF’s SAB, made the following statement regarding his recent study of valproic acid and NPC:

We have just concluded our mouse studies on valproic acid and have evaluated its effect on cells from a number of NPC patients and on the NPC mouse. Unfortunately, the results are not great.

• For NPC patient cell lines we have treated six different lines with valproate. Some cells responded positively; i.e., the cholesterol storage was cleared but some lines were completely resistant to the treatment. Upon analysis of our data it became clear that if the patient has a relatively mild mutation then they would respond to valproate, whereas if the mutation is more severe, then the cells don’t respond.

•With respect to the mouse study, we have treated about 25 mice with daily dosing of valproate. We can extend the life of these mice by about 10%. The mice live about 122 days on average vs. 108 days for the untreated mice.

At this point we don’t think that valproic acid would be beneficial for NPC patients.

Some years ago, valproic acid was given to a few NPC patients, including Stacey Vorpahl (1985-2004), the daughter of Gary and Barbara Vorpahl of Fort Atkinson, Wisconsin for the treatment of seizures. Barb, Vice Chair of the NNPDF Board of Directors, recently posted to the NNPDF listserv group about her family’s experience with valproic acid (as Depakote):

We did have Stacey on valproic acid (Depakote) for seizures when she first started having seizures. This was at age seven. Once she started Depakote we saw a rapid decline. One of the side effects is muscle weakness. It can also actually cause seizures at higher doses. She was on Depakote for about a year. She quit talking, needed a wheelchair, could no longer sit up or roll over by herself. We didn’t think she would survive to age 8 at her rate of deterioration. We thought the decline was from NPC but after comparing notes with other parents and seeing strange seizures that their children were also experiencing when doses were increased, we decided to gradually wean her off of Depakote and try another seizure medication. It was like bringing her back from the dead. We saw her strength start coming back, alertness level [sic], her talking never resumed but she did have strength to walk with assistance. I know others have had success with valproic acid but for Stacey it was a very negative experience. I was very surprised when I saw research coming out on valproic acid. It may work in mice but it certainly did not help our daughter even controlling seizures.

This summary was compiled by the NNPDF Central Office staff with thanks to the members of our esteemed Scientific Advisory Board. (March 31, 2011)

The National Niemann-Pick Disease Foundation (NNPDF) does not engage in the practice of medicine. It is not a medical authority nor does it claim to have medical knowledge. This site is an educational service of the National Niemann-Pick Disease Foundation and is not meant to provide diagnostic or treatment advice. Information contained or suggested on this Web site does not constitute medical advice. For all information related to care, medication or treatment, the NNPDF recommends consulting a physician to determine if information presented is applicable. Please review these additional cautions about medical information provided on the Internet.

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