Neurology -- Correspondence for Ravina et al., 60 (8) 1234-1240

Correspondence published:

Reply to Letter to the Editor: Bernard Ravina, Susan Fagan, Robert Hart, Collin Hovinga, Diane Murphy, Ted Dawson, and John Marler (1 July 2003)

Neuroprotective agents for clinical trials in Parkinson’s disease: A systematic assessment: F Tison, E Diguet, N Stefanova, CE Gross, GK Wenning and E Bezard (1 July 2003)

Reply to Letter to the Editor 1 July 2003

Bernard Ravina,
Neuroscience Center
Neurogenetics Branch 6001 Executive Boulevard Room 2225 Rockville MD 20892 9267,
Susan Fagan, Robert Hart, Collin Hovinga, Diane Murphy, Ted Dawson, and John Marler
Send Correspondence to journal:
Re: Reply to Letter to the Editor

RavinaB{at}ninds.nih.gov Bernard Ravina, et al.

We appreciate the input of Diguet et al. and strongly encourage the submission of all relevant information on potential drugs for PD to the committee to identify neuroprotective agents (CINAPS). However, published data clearly support pilot studies of minocycline in PD at this time.
The comments from Diguet et al. raise several issues about the way drugs are selected for testing in clinical trials. The CINAPS process emphasized the need for consistent pre-clinical results. [1] This is a higher level of evidence than is often used in drug selection and drugs are often selected for trials on the basis of a single positive pre- clinical study. Minocycline has been shown to have neuroprotective effects in published studies of MPTP [2, 3] and six OHDA [4] treated rodents, transgenic rodent models of both ALS [5, 6, 7, 8] and HD, [9, 10] and in excitotoxicity models. [11, 12] The mechanisms of inhibition of glial activation and apoptosis are relevant in PD and minocycline achieves concentrations in the CNS necessary for neuroprotection. [1, 3, 13, 14] These data clearly support the use of minocycline in PD.
In the interest of objectivity, the CINAPS process included only data published in peer-reviewed journals for non-proprietary compounds. We strongly encourage the publication of negative studies, but Diguet et al's letter provides an incomplete account of their experiments and unpublished studies such as these are difficult to evaluate fully. The details of the experimental design as well as the results are not fully disclosed. It is difficult then to speculate as to why Diguet et al. obtained results opposite those in the published literature nor do the authors offer an explanation.
The foremost responsibility of any clinical researcher is patient safety and thus we take seriously any possibility that a drug could worsen PD. Minocycline has been used clinically for decades and is currently being studied in ALS and HD without evidence that it hastens neurodegeneration. [15] The NINDS sponsored neuroprotection trials are designed specifically to evaluate safety and determine if minocycline and other agents warrant further study for efficacy.
Diguet et al. suggest that further testing of minocyline in clinical trials should not proceed. But uncertainty and even contradictory evidence are a part of clinical trials and clinical equipoise. Clinical equipoise, or uncertainty about the benefits of a drug in the research community as a whole, allows for the ethical conduct of clinical trials. Far from prohibiting further study, clinical equipoise acknowledges that new information and disagreement are a part of clinical trials. The preponderance of data strongly favors minocycline; this view is shared by the NINDS neuroprotection study steering committee (personal communication). The ultimate value of minocycline can only be determined in human studies. Delaying human study for further testing in pre- clinical models with uncertain predictive validity is unlikely to decisively determine the role of minocycline in PD.
References:
1. Ravina BM, Fagan SC, Hart RG, et al. Neuroprotective agents for clinical trials in Parkinson's disease: a systematic assessment. Neurology 2003;60:1234-1240.
2. Wu DC, Jackson-Lewis V, Vila M, et al. Blockade of microglial activation is neuroprotective in the 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine mouse model of Parkinson disease. J Neurosci. 2002;22:1763-1771.
3. Du Y, Ma Z, Lin S, Dodel RC, et al. Minocycline prevents nigrostriatal dopaminergic neurodegeneration in the MPTP model of Parkinson's disease. Proc Natl Acad Sci U S A. 2001;98:14669-14674.
4. He Y, Appel S, Le W. Minocycline inhibits microglial activation and protects nigral cells after 6-hydroxydopamine injection into mouse striatum. Brain Res. 2001;909:187-193.
5. Zhu S, Stavrovskaya IG, Drozda M, et al. Minocycline inhibits cytochrome c release and delays progression of amyotrophic lateral sclerosis in mice. Nature. 2002;417:74-78.
6. Van Den Bosch L, Tilkin P, Lemmens G, Robberecht W. Minocycline delays disease onset and mortality in a transgenic model of ALS. Neuroreport. 2002;13:1067-1070.
7. Kriz J, Nguyen MD, Julien JP. Minocycline slows disease progression in a mouse model of amyotrophic lateral sclerosis. Neurobiol Dis. 2002;10:268-278.
8. Zhang W, Narayanan M, Friedlander RM. Additive neuroprotective effects of minocycline with creatine in a mouse model of ALS. Ann Neurol. 2003;53:267-270.
9. Chen M, Ona C, Li M, Ferrante R, et al. Minocycline inhibits caspase-1 and caspase-2 expression and delays mortality in a transgenic mouse model of Huntington disease. Nature Medicine. 2000;6:797-801.
10. Berger A. Minocycline slows progress of Huntington's disease in mice BMJ. 2000;321:70.
11. Tikka T, Fiebich BL, Golsteins G, et al. Minocycline, a Tetracycline Derivative, Is Neuroprotective against Excitotoxicity by Inhibiting Activation and Proliferation of Microglia. J. Neurosci. 2001;21:2580-2588.
12. Tikka TM, Koistinaho JE. Minocycline provides neuroprotection against N-methyl-D-aspartate neurotoxicity by inhibiting microglia. J Immunol. 2001;166:7527-7533.
13. Thomas M, Le WD, Jankovic J. Minocycline and other tetracycline derivatives: a neuroprotective strategy in Parkinson's disease and Huntington's disease. Clin Neuropharmacol. 2003;26:18-23. Review
14. Friedlander RM. Apoptosis and caspases in neurodegenerative diseases. N Engl J Med 2003;348:1365-1375.
15. Bonelli RM, Heuberger C, Reisecker F. Minocycline for Huntington's disease: An open label study. Neurology. 2003;60:883-884.

Neuroprotective agents for clinical trials in Parkinson’s disease: A systematic assessment 1 July 2003

F Tison,
Universite Victor Segalen-Bordeaux2
146 rue Leo-Saignat Bordeaux France 33076,
E Diguet, N Stefanova, CE Gross, GK Wenning and E Bezard
Send Correspondence to journal:
Re: Neuroprotective agents for clinical trials in Parkinson’s disease: A systematic assessment

francois.tison{at}chu-bordeaux.fr F Tison, et al.

We read with interest the special article by Ravina et al. proposing neuroprotective candidate drugs for clinical trials in Parkinson's disease (PD). [1] Minocycline, which has already been launched for phase II/III trials in PD, Huntington's disease (HD) and atypical parkinsonism is one of the 21 selected drugs that passed a set of pre-defined evaluation criteria: primary mechanism(s), consistency of preclinical data, BBB penetration, safety/tolerability ratio and relevant animal model efficacy. The pharmacokinetics and mechanisms of anti-inflammatory/anti-apoptotic actions of minocycline are well known. [1] There are some evidences that minocycline might confer neuroprotection in rodent models of PD-like neurodegeneration and transgenic model of HD, using various doses and routes of administration. [1, 2]
In contrast with those latter, our own experiments fail to show beneficial effects of minocycline in three different animal models (unpublished data). Using a progressive 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) non-human primate model that replicates the progressive nature of PD, [3] we observed that minocycline (200-mg b.i.d., 12 hours apart, minocycline generic) treatment had a deleterious effect. Indeed, while MPTP-placebo-treated animals displayed mild parkinsonism at day 15 (mean motor score=5±0.6), the minocycline/MPTP-treated tended to be more affected (11±1.2, p=0.057, Mann-Whitney,) suggesting that minocycline/MPTP-treated animals developed symptoms more rapidly and severely.
Striatal sections from both groups were processed at day 15 for dopamine transporter binding, [2] compared to control animals. The minocycline/MPTP-placebo-treated animals showed a greater loss of striatal dopaminergic nerve endings than MPTP-treated animals (e.g. in dorsal caudate at the rostral level, - 76% and -54.5% in comparison with controls (p<0.0001, ANOVA). We also investigated the effect of minocycline (minocycline HCl, Sigma, 45mg/kg b.i.d in saline, i.p.) in the systemic subacute 3-nitropropionic acid (3-NP) model of HD in the C57Bl/6 mice (n=8: 3-NP + minocycline, n=8: 3-NP + saline, n=8: saline + saline controls). [4] The minocycline-treated group was significantly more behaviorally impaired, from day 5 onwards (at the end of the 3-NP intoxication period, total dose of 3-NP=360 mg) until sacrifice at day 13 (3-NP + minocycline= 2.6+0.1 vs. 3-NP + saline=1.0+0.1, p<0.0001, vs. controls 0.2+0.05, p< 0.0001, Mann-Whitney).
During the first week after 3-NP intoxication the behavioral performance of minocycline-treated mice as measured by rotarod, pole test, traversing a beam tasks and general activity parameters was also significantly decreased (p<0.05 compared to 3-NP alone and controls, unpaired t-Test). Not surprisingly, striatal cell loss was more severe in the minocycline-treated mice. Interactions between minocycline and 3-NP were excluded by the study of brain SDH (mitochondrial complex II) inhibition. In the third experiment we studied the effect of minocycline (15 mg/kg b.i.d) in the "double toxin-double lesion" rat model of striatonigral degeneration (SND/MSA-P), using sequential stereotactic injection of 6-hydroxydopamine (6OHDA) in the medial forebrain bundle (MFB) and quinolinic acid (QA) in the striatum. [5] Wistar rats randomly selected in minocycline treated (n = 15) and untreated groups (n = 15) received stereotaxic QA injection (90 nmol) into the left striatum and 3 days later 6OHDA (8 µg) in the left MFB. Minocycline treated animals were injected i.p. prior the surgeries and every day for 3 weeks. Minocycline- treated and untreated animals were not different whatever the considered parameter, i.e. locomotor activity and striatal cell loss (DARPP-32).
Although minocycline significantly suppressed astroglial (GFAP) and microglial (Ox6) activation, only a marginal neuroprotective effect at a single level of the ipsilateral substantia nigra (mean neuronal count 43.7+10.7 in the minocycline group vs. 30.7+18 in the saline group, p< 0.05, unpaired t-Test) has been observed. A stereological analysis of the whole substantia nigra failed to elicit a positive effect. Taking into account these results in three different neurodegenerative models, we disagree with Ravina et al. [1] considering that there is consistent animal experimental basis supporting neuroprotective effects of minocycline in PD, HD and atypical parkinsonism. We believe that additional experimental work should be considered to establish the scope and consistency of minocycline neuroprotective effects in neurodegenerative basal ganglia disorders before embarking in further clinical trials.
References:
1. Ravina BM, Fagan SC, Hart RG, et al. Neuroprotective agents for clinical trials in Parkinson's disease: a systematic assessment. Neurology 2003;60:1234-1240.
2. Thomas M, Dong W, Jankovic J. Minocycline and other tetracycline derivates: A neuroprotective strategy in Parkinson's disease and Huntington's disease. Clin Neuropharm 2003;26:18-23.
3. Bezard E, Dovero S, Prunier C, et al. Relationship between the appearance of symptoms and the level of nigrostriatal degeneration in a progressive 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine-lesioned macaque model of Parkinson's disease. J Neurosci 2001; 21: 6853-6861.
4. Fernagut PO, Diguet E, Stefanova N, et al. Subacute systemic 3- nitropropionic acid intoxication induces a distinct motor disorder in adult C57BL/6 mice: behavioral and histopathological characterization. Neurosci 2002;114:1005-1017.
5. Scherfler C, Puschban Z, Ghorayeb I, et al. Complex motor disturbances in a sequential double lesion rat model of striatonigral degeneration (multiple system atrophy). Neuroscience. 2000;99:43-54.