PAK inhibitors and potentially treating some Autism using Grandpa’s Medicine Cabinet

I wrote several posts about why PAK1 inhibitors should be beneficial in some autism and indeed some schizophrenia.

We also saw that PAK1-blocking drugs could be potentially useful for the treatment of neurofibromatosis type 2, in addition to RAS-induced cancers and neurofibromatosis type 1.

One problem with drugs developed for cancer is that, even if they finally get approved, they tend to be ultra-expensive.  Production volumes are low because even if they “work” they do not prolong life for so long and cancer has numerous sub-types.

Cheap drugs are ones used to treat common chronic conditions like high blood pressure, high cholesterol and indeed treatment of male lower urinary tract symptoms (LUTS), like benign prostatic hyperplasia (BPH).

A small number of readers of this blog have confirmed the beneficial effect of PAK inhibitors in their specific sub-types of autism.  The problem is that there are no potent PAK1 inhibitors suitable for long term use that are readily available.

The anti-parasite drug Ivermectin is an extremely cheap PAK1 inhibitor, but cannot be used long term, due to its other effects.

Propolis containing CAPE (Caffeic Acid Phenethyl Ester) is a natural PAK1 inhibitor, but may not be sufficiently potent as is reported by people with neurofibromatosis.

You would think somebody would just synthesize CAPE (Caffeic Acid Phenethyl Ester) artificially and then higher doses could be achieved.

PAK Inhibitors and Treatment of Prostate Enlargement

I was rather surprised that research has recently been published suggesting that PAK inhibitors could be used to treat the prostate enlargement, common in most older men. 

P21-Activated Kinase Inhibitors FRAX486 and IPA3: Inhibition of Prostate Stromal Cell Growth and Effects on Smooth Muscle Contraction in the Human Prostate

Abstract

Prostate smooth muscle tone and hyperplastic growth are involved in the pathophysiology and treatment of male lower urinary tract symptoms (LUTS). Available drugs are characterized by limited efficacy. Patients’ adherence is particularly low to combination therapies of 5α-reductase inhibitors and α₁-adrenoceptor antagonists, which are supposed to target contraction and growth simultaneously. Consequently, molecular etiology of benign prostatic hyperplasia (BPH) and new compounds interfering with smooth muscle contraction or growth in the prostate are of high interest. Here, we studied effects of p21-activated kinase (PAK) inhibitors (FRAX486, IPA3) in hyperplastic human prostate tissues, and in stromal cells (WPMY-1). In hyperplastic prostate tissues, PAK1, -2, -4, and -6 may be constitutively expressed in catecholaminergic neurons, while PAK1 was detected in smooth muscle and WPMY-1 cells. Neurogenic contractions of prostate strips by electric field stimulation were significantly inhibited by high concentrations of FRAX486 (30 μM) or IPA3 (300 μM), while noradrenaline- and phenylephrine-induced contractions were not affected. FRAX486 (30 μM) inhibited endothelin-1- and -2-induced contractions. In WPMY-1 cells, FRAX486 or IPA3 (24 h) induced concentration-dependent (1–10 μM) degeneration of actin filaments. This was paralleled by attenuation of proliferation rate, being observed from 1 to 10 μM FRAX486 or IPA3. Cytotoxicity of FRAX486 and IPA3 in WPMY-1 cells was time- and concentration-dependent. Stimulation of WPMY-1 cells with endothelin-1 or dihydrotestosterone, but not noradrenaline induced PAK phosphorylation, indicating PAK activation by endothelin-1. Thus, PAK inhibitors may inhibit neurogenic and endothelin-induced smooth muscle contractions in the hyperplastic human prostate, and growth of stromal cells. Targeting prostate smooth muscle contraction and stromal growth at once by a single compound is principally possible, at least under experimental conditions.

It looks like a PAK inhibitor could potentially solve both the key problems in BPH and so replace the current therapies.

Existing Drugs for LUTS/BPH

Undoubtedly someone is going to wonder whether existing drugs for LUTS/BPH might improve autism.  This is actually possible, but totally unrelated to PAK1 inhibition and RASopathies.

Existing drugs are in two classes, 5α-reductase inhibitors and α₁-adrenoceptor antagonists.

α-adrenoceptor antagonists

Alpha blockers relax certain muscles and help small blood vessels remain open. They work by keeping the hormone norepinephrine (noradrenaline) from tightening the muscles in the walls of smaller arteries and veins, which causes the vessels to remain open and relaxed. This improves blood flow and lowers blood pressure.

Because alpha blockers also relax other muscles throughout the body, these medications can help improve urine flow in older men with prostate problems.

Selective α₁-adrenergic receptor antagonists are often used in BPH because it is the α₁-adrenergic receptor that is present in the prostate.

 α ₂-adrenergic receptors are present elsewhere in the body

Alpha-2 blockers are used to treat anxiety and post-traumatic stress disorder (PTSD). They decrease sympathetic outflow from the central nervous system. Post-traumatic stress disorder is an anxiety disorder that is theorized to be related to a hyperactive sympathetic nervous system.

Alpha-2 receptor agonists for the treatment of post-traumatic stress disorder

So a nonselective alpha blocker, like one given to an older man with high blood pressure and BPH, might well have an effect on some kinds of anxiety.

You would think that a selective alpha 2 blocker might be interesting, how about Idazoxan?

Idazoxan is a drug which is used in research. It acts as both a selective α2 adrenergic receptor antagonist, and an antagonist for the imidazoline receptor. Idazoxan has been under investigation as an antidepressant, but it did not reach the market as such. More recently, it is under investigation as an adjunctive treatment in schizophrenia. Due to its alpha-2 receptor antagonism it is capable of enhancing therapeutic effects of antipsychotics, possibly by enhancing dopamine neurotransmission in the prefrontal cortex of the brain, a brain area thought to be involved in the pathogenesis of schizophrenia.

Mirtazapine is a cheap generic drug used at high doses for depression.  It happens to be a selective alpha 2 blocker, but it has numerous other effects as well.  One reader of this blog does respond very well to Mirtazapine.

So realistically in Grandpa’s medicine cabinet there might a selective alpha 1 agonist or a non-selective alpha agonist, it is the latter type that might have an effect on some kinds of autism.

5α-reductase inhibitors

The pharmacology of 5α-reductase inhibition involves the binding of NADPH to the enzyme followed by the substrate. Specific substrates include testosterone, progesterone, androstenedione, epitestosterone, cortisol, aldosterone, and deoxycorticosterone.

Beyond being a catalyst in testosterone reduction, 5α-reductase isoforms I and II reduce progesterone to 5α-dihydroprogesterone (5α-DHP) and deoxycorticosterone to dihydrodeoxycorticosterone (DHDOC).

In vitro and animal models suggest subsequent 3α-reduction of DHT, 5α-DHP and DHDOC lead to neurosteroid metabolites with effect on cerebral function.

These neurosteroids, which include allopregnanolone, tetrahydrodeoxycorticosterone (THDOC), and 5α-androstanediol, act as potent positive allosteric modulators of GABA_A receptors, and have anticonvulsant, antidepressant, anxiolytic, prosexual, and anticonvulsant effects.

Inhibition of 5α-reductase results in decreased conversion of testosterone to DHT.

This, in turn, results in slight elevations in testosterone and estradiol levels. 

In BPH, DHT acts as a potent cellular androgen and promotes prostate growth; therefore, it inhibits and alleviates symptoms of BPH. In alopecia, male and female-pattern baldness is an effect of androgenic receptor activation, so reducing levels of DHT also reduces hair loss.

A new look at the 5alpha-reductase inhibitor finasteride

Finasteride is the first 5alpha-reductase inhibitor that received clinical approval for the treatment of human benign prostatic hyperplasia (BPH) and androgenetic alopecia (male pattern hair loss). These clinical applications are based on the ability of finasteride to inhibit the Type II isoform of the 5alpha-reductase enzyme, which is the predominant form in human prostate and hair follicles, and the concomitant reduction of testosterone to dihydrotestosterone (DHT). In addition to catalyzing the rate-limiting step in the reduction of testosterone, both isoforms of the 5alpha-reductase enzyme are responsible for the reduction of progesterone and deoxycorticosterone to dihydroprogesterone (DHP) and dihydrodeoxycorticosterone (DHDOC), respectively. Recent preclinical data indicate that the subsequent 3alpha-reduction of DHT, DHP and DHDOC produces steroid metabolites with rapid non-genomic effects on brain function and behavior, primarily via an enhancement of gamma-aminobutyric acid (GABA)ergic inhibitory neurotransmission. Consistent with their ability to enhance the action of GABA at GABA(A) receptors, these steroid derivatives (termed neuroactive steroids) possess anticonvulsant, antidepressant and anxiolytic effects in addition to altering aspects of sexual- and alcohol-related behaviors. Thus, finasteride, which inhibits both isoforms of 5alpha-reductase in rodents, has been used as a tool to manipulate neuroactive steroid levels and determine the impact on behavior. Results of some preclinical studies and clinical observations with finasteride are described in this review article. The data suggest that endogenous neuroactive steroid levels may be inversely related to symptoms of premenstrual and postpartum dysphoric disorder, catamenial epilepsy, depression, and alcohol withdrawal.

This would suggest that a 5α-reductase inhibitor, like finasteride, that might be among Grandpa’s tablets might very well have an effect on someone with GABAa dysfunction, this includes very many people with autism, schizophrenia and Down Syndrome.

Whether the effect will be good or bad is hard to say, and may well depend on whether other drugs that target GABA or NMDA receptors are being used. Due to their other effects, 5α-reductase inhibitors are usually only used in adults.

Merck developed a lower dose form of finasteride, called Prospecia to treat baldness, usually in men.  It is 20% the normal potency used for BPH.

Side effects

The current BPH drugs cause side effects in some people.  PAK1 inhibitors may also have some side effects.

Conclusion

Going back in the days of living with your extended family might make treating many people’s autism much simpler.  It looks like many older people’s drugs can be repurposed for some types of autism (ion channel modifying diuretics, calcium channel blockers, statins, even potentially intranasal insulin in some).  Because older people’s drugs are so widely used they are well understood and inexpensive.  

Clearly the research on PAK inhibitors for LUTS/BPH is at an early stage, but there is a huge potential market.   A widely available PAK1 inhibitor might be a big help to some people with autism, neurofibromatosis, other RASopathies, not just Grandpa’s prostate.

In addition to FRAX486 and IPA3, why doesn’t someone try synthetic CAPE, i.e. without the bees, as a PAK inhibitor?

Bioactivity and chemical synthesis of caffeic acid phenethyl ester and its derivatives.

There is far more chance of a PAK1 inhibitor coming to market for LUTS/BPH, or certain cancers than for autism.  That is a fact of life.

As for 5α-reductase inhibitors, like finasteride, we know from Hardan’s study on Pregnenolone at Stanford that this hormone can have a positive effect and we know that various natural steroid metabolites will modulate GABA subunits.  So it is quite likely that finasteride is going have a behavioral effect.  Perhaps Hardan would like to trial finasteride 5mg and 1mg (Prospecia) in some adults with autism. I suspect it will make some people “worse” and others somewhat “better”; so please do not report the “average” response, highlight the nature of the positive responders.