The biotech company Acorda Therapeutics Inc. yesterday announced that it was halting new recruitment for the phase III program of its drug Tozadenant (an oral adenosine A2a receptor antagonist).
In addition, participants currently enrolled in the trial will now have their blood monitoring conducted on a weekly basis.
The initial report looks really bad (tragically five people have died), but does this tragic news mean that the drug should be disregarded?
In todays post, we will look at what adenosine A2a receptor antagonists are, how they may help with Parkinson’s, and discuss what has happened with this particular trial.
Dr Ron Cohen, CEO of Acorda. Source: EndpointNews
Founded in 1995, Acorda Therapeutics Ltd is a biotechnology company that is focused on developing therapies that restore function and improve the lives of people with neurological disorders, particularly Parkinson’s disease.
Earlier this year, they had positive results in their phase III clinical trial of Inbrija (formerly known as CVT-301 – Click here to read a previous post about this). They have subsequently filed a New Drug Application with the US Food and Drug Administration (FDA) to make this inhalable form of L-dopa available in the clinic, but the application has been delayed due to manufacturing concerns from the FDA (Click here to read more about this). These issues should be solvable – the company and the FDA are working together on these matters – and the product will hopefully be available in the new year.
So what was the news yesterday?
Acorda Therapeutics has another experimental product going through the clinical trial process for Parkinson’s disease.
It’s called Tozadenant.
Tozadenant is an oral adenosine A2a receptor antagonist (and yes, we’ll discuss what all that means in a moment).
Yesterday Acorda Therapeutics Inc announced that they have halted new recruitment for their phase III clinical program. In addition the company is increasing the frequency of blood cell count monitoring (from monthly to weekly) for participants already enrolled in the company’s Phase 3 program of Tozadenant for Parkinson’s disease.
The Company took this action due to reports of cases of agranulocytosis.
Today there was a lot of Parkinson’s related activity in the news… well, more than usual at least.
Overnight there was the publication of a blood test for Parkinson’s disease, which looks very sensitive. And this afternoon, Acorda Therapeutics announced positive data for their phase three trial.
In this post, we’ll look at what it all means.
Blood cells. Source: Reference.com
Today we found out about an interesting new study from scientists at Lund University (Sweden), where they are developing a test that can differentiate between different types of Parkinsonisms (See our last post about this) using a simple blood test.
We have previously reported about an Australian research group working on a blood test for Parkinson’s disease, but they had not determined whether their test could differentiate between different kinds of neurodegenerative conditions (such as Alzheimer’s disease). And this is where the Swedish study has gone one step further…
Title: Blood-based NfL: A biomarker for differential diagnosis of parkinsonian disorder
Authors: Hansson O, Janelidze S, Hall S, Magdalinou N, Lees AJ, Andreasson U, Norgren N, Linder J, Forsgren L, Constantinescu R, Zetterberg H, Blennow K, & For the Swedish BioFINDER study
Journal: Neurology, Published online before print February 8, 2017
PMID: N/A (This article is OPEN ACCESS if you would like to read it)
The research group in Lund had previously demonstrated that they could differentiate between people with Parkinson’s disease and other types of Parkinsonism to an accuracy of 93% (Click here to read more on this). That is a pretty impressive success rate – equal to basic clinical diagnostic success rates (click here for more on this).
The difference was demonstrated in the levels of a particular protein, neurofilament light chain (or Nfl). NfL is a scaffolding protein, important to the cytoskeleton of neurons. Thus when cells die and break up, Nfl could be released. This would explain the rise in Nfl following injury to the brain. Other groups (in Germany and Switzerland) have also recently published data suggesting that Nfl could be a good biomarker of disease progression (Click here to read more on this).
There was just one problem: that success rate we were talking about above, it required cerebrospinal fluid. That’s the liquid surrounding your brain and spinal cord, which can only be accessed via a lumbar puncture – a painful and difficult to perform procedure.
Lumbar puncture. Source: Lymphomas Assoc.
Not a popular idea.
This led the Swedish researchers to test a more user friendly approach: blood.
In the current study, the researchers took blood samples from three sets of subjects:
- A Lund set (278 people, including 171 people with Parkinson’s disease (PD), 30 people with Multiple system atrophy (MSA), 19 people with Progressive Supranuclear Palsy (PSP), 5 people with corticobasal syndrome (CBS), and 53 people who were neurologically healthy (controls).
- A London set (117 people, including 20 people with PD, 30 people with MSA, 29 people with PSP, 12 people with CBS, and 26 neurologically healthy controls
- An early disease set (109 people, including 53 people with PD, 28 people with MSA, 22 people with PSP, 6 people with CBS). All of the early disease set had a disease duration less than 3 years.
When the researchers looked at the levels of NfL in blood, they found that they could distinguish between people with PD and people with PSP, MSA, and CBS with an accuracy of 80-90% – again a very impressive number!
One curious aspect of this finding, however, is that the levels of Nfl in people with PD are very similar to controls. So while this protein could be used to differentiate between PD and other Parkinsonisms, it may not be a great diagnostic aid for determining PD verses non-PD/healthy control.
In addition, what could the difference in levels of Nfl between PD and other Parkinsonisms tell us about the diseases themselves? Does PD have less cell death, or a more controlled and orderly cell death (such as apoptosis) than the other Parkinsonisms? These are questions that can be examined in follow up work.
Like we said at the top, it’s been a busy day for Parkinson’s disease: Good news today for Acorda Therapeutics, Inc.
They announced positive Phase 3 clinical trial results for their inhalable L-dopa treatment, called CVT-301, which demonstrated a statistically significant improvement in motor function in people with Parkinson’s disease experiencing OFF periods.
We have previously discussed the technology and the idea behind this approach to treating Parkinson’s disease (Click here for that post).
The ARCUS inhalation technology. Source: ParkinsonsLife
Basically, the inhaler contains capsules of L-dopa, which are designed to break open so that the powder can escape. By sucking on the inhaler (see image below), the open capsule starts spinning, releasing the levodopa into the air and subsequently into the lungs. The lungs allow for quicker access to the blood system and thus, the L-dopa can get to the brain faster. This approach will be particularly useful for people with Parkinson’s disease who have trouble swallowing pills/tablets – a common issue.
The Phase 3, double-blind, placebo-controlled clinical trial evaluated the efficacy and safety of CVT-301 when compared with a placebo in people with Parkinson’s disease who experience motor fluctuations (OFF periods). There were a total of 339 study participants, who were randomised and received either CVT-301 or placebo. Participants self-administered the treatment (up to five times daily) for 12 weeks.
The results were determined by assessment of motor score, as measured by the unified Parkinson’s disease rating scale III (UPDRS III) which measures Parkinson’s motor impairment. The primary endpoint of the study was the amount of change in UPDRS motor score at Week 12 at 30 minutes post-treatment. The change in score for CVT-301 was -9.83 compared to -5.91 for placebo (p=0.009). A negative score indicates an improvement in overall motor ability, suggesting that CVT-301 significantly improved motor score.
The company will next release 12-month data from these studies in the next few months, and then plans to file a New Drug Application (NDA) with the Food and Drug Administration (FDA) in the United States by the middle of the year and file a Marketing Authorization Application (MAA) in Europe by the end of 2017. This timeline will depend on some long-term safety studies – the amount of L-dopa used in these inhalers is very high and the company needs to be sure that this is not having any adverse effects.
All going well we will see the L-dopa inhaler reaching the clinic soon.
The banner for today’s post was sourced from the Huffington Post
For more than 50 years, L-dopa (a critical ingredient used by the brain to produce the chemical dopamine) has been one of the primary therapies used in the treatment of Parkinson’s disease. Over those years, there have been several different versions of L-dopa, providing advantages over previous forms. Last week, the results of clinical trials involving a new inhalable version of L-dopa were published.
In this post we will review the results of those studies.
Inhalers. Source: Verywell
The motor features (a resting tremor in one of the limbs, slowness of movement, and rigidity in the limbs) of Parkinson’s disease begin to appear when most of the dopamine producing neurons in the brain have been lost (specifically, >60% of the midbrain dopamine neurons). Thus for the last 50 years the primary means of treating Parkinson’s disease has been via dopamine replacement therapies.
Why don’t we just inject people with dopamine?
The chemical dopamine has a very difficult time crossing the blood-brain barrier, which is a thick membrane surrounding the brain. This barrier protects the brain from unwanted undesirables (think toxic chemicals), but it also blocks the transfer of some chemicals that exert a positive impact (such as dopamine).
When dopamine is blocked from entering the brain, other enzymes can convert it into another chemical called ‘norepinephrine’ (or epinephrine) and this conversion can cause serious side effects in blood pressure and glucose metabolism.
In addition, any dopamine that does find its way into the brain is very quickly broken down by enzymes. Thus, the amount of time that dopamine has to act is reduced, resulting in a very limited outcome. And these reasons are why doctors turned to L-dopa instead of dopamine in the treatment of Parkinson’s disease.
What is L-dopa?
Basically, Levodopa (L-dopa) is a chemical intermediary in the production of dopamine. That is to say, you need L-dopa to make dopamine. L-dopa is very stable inside the body and crosses the blood-brain-barrier very easily.
In the UK, a commonly used version is known as ‘Sinemet®‘(produced by Merck).
The chemical structure of L-dopa. Source: Wikipedia
The best way to understand what L-dopa is probably be to explain the history of this remarkable chemical.
The history of L-dopa
Until the 1950s there were few treatment options for Parkinson’s disease, but a young scientist in Sweden was about to change that.
This is Arvid Carlsson.
Prof Arvid Carlsson. Source: Alchetron
He’s a dude.
In 1957, he discovered that when he injected the brains of rabbits with a neurotoxin (reserpine) it killed the dopamine neurons (and the animals exhibited reduced movement). He also discovered that by injecting the dopamine precursor –L-dopa – into those same animals, he was able to rescue their motor ability. Importantly, he found that the serotonin precursor (called 5-hydroxytryptophan) was not capable of reversing the reduction in motor ability, indicating that the effect was specific to L-dopa.
Here is the 1957 report:
Title: 3,4-Dihydroxyphenylalanine and 5-hydroxytryptophan as reserpine antagonists.
Authors: Carlsson A, Lindqvist M, Magnusson T.
Journal: Nature. 1957 Nov 30;180(4596):1200. No abstract available.
PMID: 13483658 (the article on the Nature website – access required)
This was a fantastic discovery. A Nobel prize winning discovery in fact.
But what to do with it?
At the time, we did not know that dopamine was depleted in Parkinson’s disease. And people with Parkinson’s continued to suffer.
It was not until 1960 that the critical discovery of Parkinson’s disease was made by another young European scientist. Carlsson’s research (and that of others) inspired the Austrian researcher, Oleh Hornykiewicz to look at dopamine levels in people with Parkinson’s disease.
And what he found changed everything.
Prof Oleh Hornykiewicz. Source: Kurienwissenschaftundkunst
In his study, Hornykiewicz found very high levels of dopamine in the basal ganglia of normal postmortem adult brains, but a marked and consistent reduction (approx. 10-fold) in six postmortem cases of Parkinsonisms. The basal ganglia is one of the main regions of the brain that dopamine neurons communicate with (releasing dopamine there).
Title: Distribution of noradrenaline and dopamine (3-hydroxytyramine) in the human brain and their behavior in diseases of the extrapyramidal system
Authors: Ehringer H, Hornykiewicz O.
Journal: Parkinsonism Relat Disord. 1998 Aug;4(2):53-7. No abstract available.
Importantly, Hornykiewicz did not stop there.
In November 1960, Hornykiewicz approached Walther Birkmayer, a doctor at a home for the aged in Vienna, and together they began some clinical trials of L-dopa in July 1961. Birkmayer injected 50 to 150 mg intravenously in saline into 20 volunteers with Parkinsonism. In their report, Birkmayer and Hornykiewicz wrote this regarding the results:
“The effect of a single intravenous injection of l-dopa was, in short, a complete abolition or substantial relief of akinesia. Bedridden patients who were unable to sit up, patients who could not stand up when seated, and patients who when standing could not start walking performed after l-dopa all of these activities with ease. They walked around with normal associated movements, and they could even run and jump. The voiceless, aphonic speech, blurred by palilalia and unclear articulation, became forceful and clear as in a normal person. For short periods of time the people were able to perform motor activities, which could not be prompted to any comparable degree by any other known drug”
Despite their initial excitement, Birkmayer and Hornykiewicz found that the response to L-dopa was very limited in its duration. In addition, subsequent trials by others were not able to achieve similar results, with many failing to see any benefit at all.
And that was when George stepped into the picture.
Dr George Cotzias…and yes, he is holding a brain. Source: New Scientist
Dr George Cotzias was a physician working in New York who became very interested in the use of L-dopa for Parkinson’s disease. And he discovered that by starting with very small doses of L-dopa, given orally every two hours and gradually increasing the dose gradually he was able to stabilize patients on large enough doses to cause a dramatic changes in their symptoms. His studies led ultimately to the Food and Drug Administration (FDA) approving the use of L-dopa for use in PD in 1970. Cotzias and his colleagues were also the first to describe L-dopa–induced dyskinesias.
How does L-dopa work?
When you take an L-dopa tablet, the chemical will enter your blood. Via your bloodstream, it arrives in the brain where it will be absorbed by cells. Inside the cells, another chemical (called DOPA decarboxylase) then changes it into dopamine. And that dopamine is released, and that helps to alleviate the motor features of Parkinson’s disease.
The production of dopamine, using L-dopa. Source: Watcut
Outside the brain, there is a lot of DOPA decarboxylase in other organs of the body, and if this is not blocked then the effect of L-dopa is reduced in the brain, as less L-dopa reaches the brain. To this end, people with Parkinson’s disease are also given Carbidopa (Lodosyn) which inhibits DOPA decarboxylase outside of the brain (Carbidopa does not cross the blood-brain-barrier).
How does the L-dopa inhaler work?
The company behind this new product, Acorda Therapeutics, spent many years developing a powdered version of levodopa that could be delivered to the lungs. Early on in this developmental process the scientists realised a problem: while normal asthma inhalers only need to release micrograms of their medicine to the lungs, a L-dopa inhaler would need to deliver 1,000 times more than that to have any effect. The huge amounts were needed to ensure that enough L-dopa would get from the lungs into the brain to be effective. Thus, the ARCUS inhaler delivers 25 to 50 milligrams in two breaths.
The inhaler contains capsules of L-dopa, which are designed to break open so that the powder can escape. By sucking on the inhaler (see image below), the open capsule starts spinning, releasing the levodopa into the air and subsequently into the lungs.
The ARCUS inhalation technology. Source: ParkinsonsLife
Pretty straightforward, right? Nice idea, cool design, easy to use.
But does it work?
What were the results of the clinical trials?
Title: Preclinical and clinical assessment of inhaled levodopa for OFF episodes in Parkinson’s disease.
Authors: Lipp MM, Batycky R, Moore J, Leinonen M, Freed MI.
Journal: Sci Transl Med. 2016 Oct 12;8(360):360ra136.
PMID: 27733560 (This article is OPEN ACCESS if you would like to read it)
In their research report, the scientists provided data from three studies: preclinical, phase one clinical, and phase two clinical. In the preclinical work, they measured the levels of L-dopa in dogs who had inhaled levodopa powder. When they looked at blood samples, they found that levodopa levels peaked in all of the animals 2.5 min after administration. This represented a very quick route to the blood system, as dogs that were given levodopa plus carbidopa orally did not exhibit peak blood levodopa levels until 30 min after administration.
In the phase one (safety) clinical trial, 18 healthy persons were enrolled, and again comparisons were made between inhaled CVT-301 and orally administered carbidopa/levodopa. This study demonstrated that CVT-301 was safe and had a similar rapidity of action as in the preclinical dog study.
Next, the researchers conducted a phase two (efficacy) clinical study. This involve 24 people with Parkinson’s disease inhaling CVT-301 as a single 50mg dose during an OFF episode (periods of no prescribed medication). 77% of the CVT-301 treated subjects showed an increase in plasma levodopa within 10 min. By comparison, only 27% of a group of subjects taking oral doses of carbidopa/levodopa at a 25-mg/100-mg dose achieved the same levels within that time. Improvements in timed finger tapping and overall motor function (as measured by the Unified Parkinson’s Disease Rating Scale) were observed between 5 and 15 minutes after administration.
The most common adverse event was cough, but all of the coughing events were considered mild to moderate, generally occurring at the time of inhalation. In most cases, they were resolved rapidly and became less frequent after initial dosing.
So what does it all mean?
Inhalation of L-dopa may represent a novel means of treating people with Parkinson’s disease, especially those who struggle with swallowing pills. The most obvious benefit is the speed with which the subjects see results.
The amount of L-dopa being used is very high, however, and we will be interested to see the results of more long term studies before passing judgement on the inhaler approach. We’ll keep you informed as more information comes to hand.
The banner for today’s post is sourced from the BBC