Hard on the heels of something I just learned about at a recent conference, the NIMH issued a Press Release for a new clinical trial they funded.
A drug that works through the same brain mechanism as the fast-acting antidepressant ketamine briefly improved treatment-resistant patients’ depression symptoms in minutes, with minimal untoward side effects, in a clinical trial conducted by the National Institutes of Health. The experimental agent, called AZD6765, acts through the brain’s glutamate chemical messenger system.
Interesting. The background is that prior studies* have shown that the dissociative anesthetic ketamine is capable of the rapid (within hours) amelioration of depressive symptoms. Yes, ketamine. The recreational drug known as Special K and the veterinary anesthetic they've used on your pet cat or dog. Same ketamine that is approved for human use in pediatric anesthesia, emergency medicine in some cases and for tricky clinical situations.
The same ketamine that has been widely used for decades in humans and nonhuman animals. It has established efficacy, mechanism of action and a huge therapeutic index. A big distance between effective doses and the dose that will kill you. Whether effect is recreational, medical or veterinary. Meaning it is safe.
So why are the studies (cited below*) of effect in depression so exciting? Because traditional drug therapy for depression takes weeks to have effect. Weeks of daily dosing. Selective Serotonin Reuptake Inhibitors (SSRIs) like Prozac are broadly familiar to most of my Readers, I would assume. Efficacy with these front-line meds takes up to three weeks to see effect on depressive symptoms. Trouble is, some cases of depression are acutely suicidal--they may just kill themselves before any SSRI has a chance to make them feel better. And hell, who wants to wait three weeks if another med could make you feel better by tomorrow? Prior to the ketamine work, the only other thing that seemed to have such a rapid effect was ECT. Yeah, ElectroConvulsive Therapy. Which has come a loooooong way from the One Flew Over the Cuckoo's Nest era....but still. A single ketamine dosing seems quite preferable.
So.....on to the me-too drug development! Woot!
Zarate CA Jr, Mathews D, Ibrahim L, Chaves JF, Marquardt C, Ukoh I, Jolkovsky L, Brutsche NE, Smith MA, Luckenbaugh DA. A Randomized Trial of a Low-Trapping Nonselective N-Methyl-D-Aspartate Channel Blocker in Major Depression. Biol Psychiatry. 2012 Nov 30. pii: S0006-3223(12)00941-9. doi: 10.1016/j.biopsych.2012.10.019. [Epub ahead of print][Publisher, PubMed]
This AZD6765 compound is, as you might deduce from the letters, property of AstraZeneca Pharmaceuticals and indeed one of the authors lists this as his affiliation. The rest of the folks are from the NIMH intramural program which, presumably, provided the majority of the funding for the study.
The conclusions appear to be that this novel compounds, with a similar mechanism of action as ketamine worked but less well. From the Presser:
About 32 percent of 22 treatment-resistant depressed patients infused with ASD6765 showed a clinically meaningful antidepressant response at 80 minutes after infusion that lasted for about half an hour – with residual antidepressant effects lasting two days for some. By contrast, 52 percent of patients receiving ketamine show a comparable response, with effects still detectable at seven days. So a single infusion of ketamine produces more robust and sustained improvement, but most patients continue to experience some symptoms with both drugs.
However, depression rating scores were significantly better among patients who received AZD6765 than in those who received placebos. The researchers deemed this noteworthy, since, on average, these patients had failed to improve in seven past antidepressant trials, and nearly half failed to respond to electroconvulsive therapy (ECT).
So this is good. Anything that shows promise as a rapid-alleviator of depression is good by my lights.
But why is NIMH spending taxpayer dollars to develop me-too drugs? Look, I recognize that drugs within a class of pharmacological mechanism, like the SSRIs, may be differentially effective for different patients. And it is a good thing if we have more options to tailor medication to the individual patient. ADHD is another situation where an array of monoamine transporter inhibitors, including methylphenidate and amphetamine, are used with success and failure. One drug works for one patient, another works for a different patient....and they might describe the other medication as even worse than not being treated. So...great.
But make no mistake. The central feature driving me-too drug development is profit. Drug companies decide they can take a big enough slice of the market away from the market-leader to make it worth their while. Perhaps they had development in parallel and had sunk enough cost in by the time their competitor gained FDA approval that there was no turning back. Whatever. Point being that they are in it for the money and not for some noble cause of serving that subset of patients that do not gain relief from their competitor's drug.
Over the past few years the side-chatter about the ketamine effect on depression has frequently been a lament about the lack of financial motive for companies to push forward with ketamine. Push forward with specific clinical trials to gain on-label approval for the indication of depression. Push forward with marketing campaigns. Push forward with physician education and stroking like they do with their proprietary stuff.
The Zarate paper took a stab at claiming the reason for developing something else was an attempt to avoid the adverse effects of ketamine. The dissociative type effects can be unpleasant and recovery doesn't look fun. So there's some toehold there to claim one is motivated to find a "perfect" drug which somehow produces the therapeutic effect with nothing else. Color me skeptical, given what I know about existing NMDA channel blockers like ketamine (and PCP, did I mention that? Yeah, angel dust might work for depression....).
So I smell profit motive in this effort.
What I don't understand is why NIMH is involved with this. Why not just pursue the evidence body for ketamine?
*References pulled out of the paper
R.M. Berman, A. Cappiello, A. Anand, D.A. Oren, G.R. Heninger, D.S. Charney et al. Antidepressant effects of ketamine in depressed patients. Biol Psychiatry, 47 (2000), pp. 351–354
N. Diazgranados, L. Ibrahim, N.E. Brutsche, A. Newberg, P. Kronstein, S. Khalife et al. A randomized add-on trial of an N-methyl-D-aspartate antagonist in treatment-resistant bipolar depression. Arch Gen Psychiatry, 67 (2010), pp. 793–802
C.A. Zarate Jr, N.E. Brutsche, L. Ibrahim, J. Franco-Chaves, N. Diazgranados, A. Cravchik et al. Replication of ketamine’s antidepressant efficacy in bipolar depression: A randomized controlled add-on trial Biol Psychiatry, 71 (2012), pp. 939–946
G.W. Valentine, G.F. Mason, R. Gomez, M. Fasula, J. Watzl, B. Pittman et al. The antidepressant effect of ketamine is not associated with changes in occipital amino acid neurotransmitter content as measured by [(1)H]-MRS Psychiatry Res, 191 (2011), pp. 122–127
M. aan het Rot, K.A. Collins, J.W. Murrough, A.M. Perez, D.L. Reich, D.S. Charney et al. Safety and efficacy of repeated-dose intravenous ketamine for treatment-resistant depression Biol Psychiatry, 67 (2010), pp. 139–145