Epigenetics: The sins of the father

In the recent paper in Nature (2014, vol 507, p. 22-24), Virginia Hughes reports the experiments carried out by Dr Dias and Dr Ressler from the University of Atlanta in recent years. They have studied the involvement in inheritance imprints in mice as a result of a fear-based reaction associated to acetophenone. As a result, they found a larger than normal expression of M71 glomeruli receptors in their offspring’s noses. These receptors are encoded by a single gene, known as Olfr151.

This elegant, but still inconclusive cause-effect mechanism approach, brings a possible explanation to a controversial observation back to the 19th century when French biologist Jean-Baptiste Lamark pointed out the pass of acquired traits to future generations. Since then, scientists have observed this phenomenon in plants, animals and even humans.

Although some scientists are still sceptical about the transmitance method, nobody denies the phenomenon. Finding an explanation to this complex problem would involve a deeper study on reproductive biology and to study both mother and father lines over few generations.

The strong suggestion that this heriditary transmission of environmental factors is due to epigenetics, a concept introduced in the 2000’s, where there are some changes in the way that DNA is packed and expressed without altering its sequence, is one of the strong lines of thought, where chemical tags (methylation) on DNA can turn genes on and off.

But even if epigenetics is directly involved in the inheritance, through marks on the material contained in the sperm, the first question to be addressed would be to understand how the effects of environmental/ health legacy get embedded into the animal’s germ cells.

Epigenetics is still unable to explain how this observed phenomenon gets passed down through multiple generations, surviving several rounds of genetic re-programing. Other suggested agents might involve histones (proteins which has been observed that they can be passed down through generations) or short RNA molecules which role would be to latch on DNA and affect further into gene expression.

Scientists are optimistic about finding a cause-effect relationship in the years to come for a phenomenon which has proved elusive for researchers in the past hundred years.


Predicting cancer targets modulated by Ayurvedic medicines

The recent availability of databases that provide both phenotypic descriptions and the chemical structures of the constituent compounds in traditional Chinese and Indian medicines, have enabled Bender et al  (J. Chem. Inf. Model. 2013 (53) 661 – 673, DOI: 10.1021/ci3005513 , http://www.andreasbender.de/) to develop a cool algorithm to predict the mode of action (MOA) of these compounds and to predict novel protein targets for cancer therapies.

Traditional medicine has been utilised by human for thousands of years and normally viewed as complementary or alternative to mainstream therapies.  However, both Chinese and traditional Indian medicine (Ayervedic) have provided us with important drugs for instance Artemisinin an antimalarial drug and reserpine an antihypertensive drug.

From 1981 to 2007, 67% of the pharmaceuticals or new molecular entities (NMEs) introduced into the market were natural product based or a derivative there of.  These natural products often have desirable properties which make them good drugs; they are soluble despite breaking Lipinski’s Rule of Five, they embody privileged structures that are more frequently found to bind a variety of proteins in different organisms, and they are safe and well-tolerated, often having been commonly used for centuries.

However, there are major challenges that need to be resolved that enable the development of a new drug from a traditional medicine.  These include the isolation of the active constituents, the synthesis of the active constituents, the elucidation of the mode of action and finally the development of the compound as a “drug”.

The recent availability of databases that provide chemical structures and their corresponding phenotypes have enabled Bender et al to predict the MOA of compounds found in TCM and Ayurveda addressing one of these major challenges.  First they developed a classifier using bioactive compounds from the ChEMBL database, ChEMBL biological targets, ECFP_4 fingerprints for each compound and a Naïve Bayes classifier.


Figure 1: The compounds were represented using the Extended Connectivity Fingerprints, with a diameter of 4 bonds ECFP_4.  The ECPF is derived from the Morgan algorithm and was implemented in Sitegic’s Pipeline Pilot (Accelrys Inc).  Each atom identifier contains topological information on the atom that includes the number of immediate heavy atoms, the atom’s mass, its charge, the number of hydrogens attached, the valance minus the number of hydrogens and whether it is part of a ring.

This was used to predict which compound (fingerprint) would inhibit each protein target.  Then by creating fingerprints for each traditional medicine compound they could predict which protein targets they would hit.  For example they predicted the protein targets for some of the active ingredients of Panaz ginseng

FP5Figure 2:  Predicted targets for some of the active ingredients in Panax Ginseng

Next they correlated different proteins targets with different phenotypes. Predicting which molecular targets were modulated by the compounds in each different phenotype.  This enabled them to identify the protein targets most frequently modulated by Ayurvedic medicines, with possible anti-tumour effects.  The 10 most enriched protein targets are shown in the table below. The progesterone receptor currently has over 10 inhibitors with FDA approval.  Other proteins identified by this methods include regulators of other well-known cancer targets.


Figure 3:  Top 10 cancer targets in predicted to be inhibited by Ayurvedic medicines.

Promising New Frontiers for RNAi Therapy

In 2001 Elbashir and Tuschl (1) published they had managed to silence gene expression in mammalian cells using small interfering RNA (siRNA). This was the catalyst for an explosion of research using siRNA to demonstrate the effect of knocking out targets without the need to identify compounds capable of doing this job. Potentially highly specific, the opportunity to use these as therapeutics was rapidly explored. Ten years later the first clinical trials are coming through; impressively fast.

Probably the largest obstacle to therapeutic siRNA has been delivery, which often is either toxic, or not very effective – as any of us who have tried to transfect siRNA into primary cells will be able to appreciate. Advances in materials science are seemingly solving this problem encapsulating siRNA in nanoparticles, resulting in safe and effective delivery. CALAA-01 (Calando Pharmaceuticals) lead the way  being the first to deliver siRNA therapeutically demonstrating phase I efficacy and safety, as well as localisation to melanoma metastases.

One particular advantage of siRNA is that once delivery has been optimised, it is possible for several different siRNAs for different targets to be contained within on package. This could enable simultaneous delivery of different targets simultaneously effecting different aspects of the same disease, i.e. metastasis and well as tumour growth. By also hitting a known resistance pathway this duel delivery could enable the chemotherapy to be more effective.

A recently published article (2) has done just this, delivering two siRNAs in lipid nanoparticles (known as ALN-VSP) for both VEGF-A (vascular endothelial growth factor-A) and kinesin spindle protein (KSP) for the treatment of advanced solid tumours with liver metastases.  KSP is involved in cancer proliferation and VEGF-A in the growth of new blood vessels.

The study was phase I, dose escalation, on patients who had already been heavily pre-treated with chemotherapy and/or anti VEGF/VEGFR agents with the ALN-VSP administered as 15 minute IV every 2 weeks for 1 month.

The safety profile was very encouraging with ALN-VSP being generally well-tolerated with mainly low-grade fatigue, nausea and fever noted in 15-24% of patients. The lipid nanoparticle of ALN-VSP distributes primarily to the liver and spleen and the delivery was also excellent. Liver biopsies were performed on 12 patients before the first dose and then at 2 and 7 days post dose. qPCR identified VEGF siRNA present in all 12 patients and KSP siRNA present in 11 of the 12.

Of the patients treated, 7 had no disease progression (measured by computerized tomography [CT] scan) after the treatment cycles and continued onto an extension study. One patient in particular with endometrial cancer achieved a complete response after 20 months of treatment

This is clearly fantastic progress for ALN-VSP, and specifically for the handful of patients who were positively affected from participation in the trial. The results from this study also demonstrate the ability for safe delivery of multiple siRNA to specific sites tumour and this extends the promising start for these methods of siRNA delivery which may open up previously un-druggable targets.


1.           Elbashir SM, Harborth J, Lendeckel W, Yalcin a, Weber K, Tuschl T. Duplexes of 21-nucleotide RNAs mediate RNA interference in cultured mammalian cells. Nature 411: 494–8, 2001.

2.           Tabernero J, Shapiro GI, Lorusso PM, Cervantes A, Schwartz GK, Weiss GJ, Paz-Ares L, Cho DC, Infante JR, Alsina M, Gounder MM, Falzone R, Harrop J, Seila White AC, Toudjarska I, Bumcrot D, Meyers RE, Hinkle G, Svrzikapa N, Hutabarat RM, Clausen V a, Cehelsky J, Nochur S V, Gamba-Vitalo C, Vaishnaw AK, Sah DWY, Gollob J a, Burris H a. First-in-Man Trial of an RNA Interference Therapeutic Targeting VEGF and KSP in Cancer Patients with Liver Involvement. Cancer discovery (January 28, 2013). doi: 10.1158/2159-8290.CD-12-0429.




Eph in ALS

A recent publication from Van Hoecke and colleagues (Van Hoecke et al., 2012) suggests a novel therapeutic approach to the treatment of amyotrophic lateral sclerosis (ALS; also called Lou Gehrig’s disease). ALS is a progressive degenerative disorder that affects 1-2/100,000 people per year and results in death, normally by respiratory failure, 3-5 years after onset. It is caused by a loss of the motor neurons that control muscle movement. There is a hereditary component in about 10% of all ALS cases and in these familial ALS subjects, a variety of genes have been implicated (Al Chalabi et al., 2012), including SOD1, TARDBP and FUS and which encode superoxide dismutase 1 (SOD-1; which was the initial gene reported to be associated with familial ALS in 1993) TAR DNA binding protein (TDP-43) and the Fused in Sarcoma protein, respectively. Recently, a hexanucleotide repeat expansions that occurs in the chromosome 9 open-reading frame 72 gene (C9ORF72) has been described to be associated with ALS with frontotemporal dementia (DeJesus-Hernandez et al, 2011; Renton et al, 2011).

The huge advances in our understanding of the genetics underlying the familial form of ALS have yet to result in breakthrough therapies for this disorder and Riluzole remains the only FDA-approved treatment for ALS. It was approved in 1995 on the basis of clinical studies that demonstrated that it increased survival times in patients, yet the effects are relatively modest and there is a clear need for new and improved treatments for ALS. Since Riluzole was approved, there have been over 30 clinical trials of new treatments but for a variety of reasons (including poor clinical trial design and drug delivery or dose selection issues) none have reached the market, although dexpramipexole, which enhances mitochondrial function, is currently undergoing Phase III trials sponsored by Knapp (Cudcowicz et al, 2011).

A key challenge to the development of new drugs based upon the genetic information derived from familial ALS, as well as genes associated with sporadic ALS, is to understand how mutations in the various genes produce a similar clinical and pathological phenotype. In other words, what is the final common pathway by which these genetic mutations produce ALS? Generic explanations such as mitochondrial dysfunction or alterations in protein degradation pathways have been suggested but how these processes are affected by genetic influences remain vague. However, it is not necessary to understand the mechanism if one can develop a screen that rescues the phenotype produced by different mutations, and this is what Van Hoecke and colleagues did. Hence, they screened for different morpholinos (antisense oligos in which ribose or deoxyribose is replaced by a morpholine ring) that rescued a SOD-1 induced axonopathy in zebra fish. The most protective morpolino targeted the zebra fish Rtk2 gene, which has 67% identity to the human EPHA4 gene that encodes for the Epha4 receptor tyrosine kinase that can bind both type A and type B ephrins. Knock down of the Rtk2 gene rescued the phenotype in zebra fish with various SOD1 mutants (A4V, G37R and G93A) and SOD-1-induced axonopathy could also be rescued pharmacologically by inhibition of Epha4 using 2,5-dimethylpyrrolyl benzoic acid.  Importantly, knockdown of Rtk1, which is a paralog with 83% identity to human Epha4, was able to rescue the axonopathy induced by either mutant SOD-1, TDP-43 or knockdown of Smn1 in zebra fish, indicating that inhibition of EphA4 is protective against motor neuron degeneration irrespective of the genetic determinant of vulnerability. Having identified Epha4 as a potential modifier of SOD1-mediated pathology, the authors also studied the effects of a deletion of the Epha4 gene in mice overexpressing the G93A mutant SOD1 and were able to show that in heterozygotes, a 50% reduction in Epha4 was able to prolong survival.

As regards ALS itself, EphA4 mRNA expression in total blood was inversely collected to the age of onset such that patients with lower levels of EphA4 expression had an age of onset older than those with higher levels of expression. Suggesting that reduced EphA4 expression is associated with a reduced disease severity. Collectively, these data shed light onto an intriguing pathway in which rescue of the axonopathy is achieved irrespective of the genetic cause. A further understanding of the mechanism by which Epha4 exerts these effects could provide the basis for novel therapeutic approaches to treating ALS.


Al-Chalabi, A., Jones, A., Troakes, C., King, A., Al-Sarraj, S. and van den Berg, L.H. (2012) The genetics and neuropathology of amyotrophic lateral sclerosis. Acta Neuropathol., 124:339-352.

Cudkowicz, M., Bozik, M.E., Ingersoll, E.W., Miller, R., Mitsumoto, H., Shefner, J., Moore, D.H., Schoenfeld, D., Mather, J.L., Archibald, D., Sullivan, M., Amburgey, C., Moritz, J. and Gribkoff, V.K. (2011) The effects of dexpramipexole (KNS-760704) in individuals with amyotrophic lateral sclerosis. Nat. Med., 17:1652-1656.

DeJesus-Hernandez, M., Mackenzie, I.R., Boeve, B.F., et al. (2011) Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS. Neuron, 72:245-256.

Renton, A.E., Majounie, E., Waite, A., et al., A hexanucleotide repeat expansion in C9ORF72 is the cause of chromosome 9p21-linked ALS-FTD. Neuron, 72:257-268.

Van Hoecke, A., Schoonaert, L., Lemmens, R., Timmers, M., Staats, K.A., Laird, A.S., Peeters, E., Philips, T., Goris, A., Dubois, B., Andersen, P.M., Al-Chalabi, A., Thijs, V., Turnley, A.M., van Vught, P.W., Veldink, J.H., Hardiman, O., Van Den Bosch, L., Gonzalez-Perez, P., Van Damme, P., Brown, R.H. Jr., van den Berg, L.H. and Robberecht, W. (2012) EPHA4 is a disease modifier of amyotrophic lateral sclerosis in animal models and in humans. Nat. Med., Aug 26. doi: 10.1038/nm.2901. [Epub ahead of print]

Bapineuzumab in Alzheimer’s Disease – Keep Calm and Carry On

The news from Pfizer released on the 23rd July stating that Bapineuzumab failed the first of four Phase III studies in Alzheimer’s Disease (AD) might have induced a wailing and gnashing of teeth and Henny Penny behaviour in certain quarters but now is not the time to panic, the sky is not falling (yet). The press release stated that in a Phase III study of 18-month duration in around 1,100 mild-to-moderate Alzheimer’s Disease (AD) patients, Bapineuzumab failed to meet either of its primary endpoints which were a significant improvement relative to placebo in cognitive performance measured using the Alzheimer’s Disease Assessment Scale-Cognitive subscale (ADAS-Cog) and functional outcomes assessed using the Disability Assessment for Dementia (DAD) scale. Nevertheless, there were signs that Bapineuzumab was having some effect, albeit with respect to side effects rather than efficacy, in that the most commonly observed, treatment-related serious adverse events were the so-called amyloid-related imaging abnormalities-edema (or ARIA-E) observed by MRI.

Bapineuzumab is a humanized version of the mouse monoclonal antibody 3D6 which recognizes the N-terminus of amyloid-β and is administered by intravenous infusion. It is being co-developed by Pfizer and Janssen Alzheimer Immunotherapy (the latter of which is a division of the healthcare giant Johnson and Johnson that acquired rights from Elan – a pharmaceutical company headquartered in Dublin – to co-develop bapineuzumab in September 2009). The rationale is that the small amount of antibody that crosses the blood-brain barrier will bind to amyloid-β within the brain and facilitate its removal by microglial-mediated phagocytosis. It is therefore a passive amyloid-β immunotherapy in which the antibody is administered directly to the patient. This distinguishes Bapineuzumab from a previous active immunization approach with Elan’s AN1792 in which the synthetic, pre-aggregated 42-amino acid amyloid-β peptide was administered along with a immunogenic adjuvant (QS-21) to stimulate an immune response in patients who then themselves produced antibodies against amyloid. Unfortunately, however, 6% of patients developed meningoencephalitis (Orgogozo et al., 2003, Neurology 61:46-54), possibly as a consequence of a pro-inflammatory T-cell response.

Before discussing the implications of the recently-released data on Bapineuzumab, it is worth considering the current state of AD therapeutics. Treatment of the symptoms associated with Alzheimer’s Disease is dominated by the cholinesterase inhibitors donepezil (tradename Aricept), galantamine (Reminyl or Razadyne) and rivastigmine (Exelon) plus the N-methyl-D-aspartate (NMDA) receptor antagonist memantine (Ebixa or Namenda). Although approved for the symptomatic treatment of Alzheimer’s Disease, these cognition-enhancing therapies leave a lot to be desired both in terms of efficacy and tolerability. Consequently, the Holy Grail for the treatment of Alzheimer’s Disease is the prevention or reversal of this debilitating disease of the elderly but unfortunately this remains a distant objective. However, a more achievable goal, a Grail of Significant (if not quite religious) Importance if you will, is that of slowing disease progression. In order to modify the disease process, it is necessary to  understand the underlying pathological processes. In this regard, we are fortunate (although that term always seems inappropriate for such a dreadful disease) to have clues from the pathological hallmarks of the disease which Alois Alzheimer first described over a hundred years ago, namely the extracellular deposits of amyloid that comprise the senile plaque and the intracellular accumulations of hyperphosphorylated tau (a protein that ordinarily plays an important part in maintaining the microtubules that comprise the scaffolding of the neuron).

There is much discussion over the relative importance of the role of amyloid-β peptide versus tau in the disease process, resulting in the moniker of BAPtists (βamyloid peptide-ists) for those believing that the abnormal production of the amyloid-β peptide from the amyloid precursor protein (APP) is the primary pathological process whereas those espousing the importance of the tau protein abnormalities comprise the tauist camp. Although the BAPtist and tauist labels makes for a linguistically convenient division in research activities it is clearly a gross oversimplification since the two pathologies must clearly be linked albeit in a manner that is currently unclear. Nevertheless, it would be fair to say that over the last 20 years or so, the BAPtists have taken the lion’s share of the spotlight based on the convincing genetic evidence that familial AD is associated with mutations in either APP or one of the subunits (either presenilin 1 or presenilin 2) that constitute the γ-secretase enzyme which, along with a second enzyme, the β-site APP cleaving enzyme type 1 (BACE1), plays a role in cleaving APP to produce β-amyloid.

Anyway, back to Bapineuzumab and the pressing question of what the recently-announced failure of the Phase III study with Bapineuzumab actually means for the amyloid hypothesis. Well, not a lot actually. First of all, the data relate to one of four Phase III currently underway and although Study 302 is the first for which data has been publically announced, it is not the key clinical trial. Hence, the AD patients in Study 302 had an ApoE4 genotype yet the Phase II data for Bapineuzumab (Salloway et al., 2009, Neurology, 73:2061-2070) showed that in this patient population, there was no effect; Phase II efficacy was only observed in those patients that did not possess the ApoE4 genotype and it is therefore data from the two Phase III studies with these non-carrier patients (Study 301 primarily based within the US and Study 3000 based primarily outside the US) that are of greatest interest. Data from Studies 301 and 302 will be presented at the Stockholm meeting of the European Federation of Neurological Sciences to be held from 8-11th September so within the next few weeks the future of Bapineuzumab should become clearer.

It is currently an important time for the amyloid hypothesis since Phase III data for the Eli Lilly antibody Solanezumab (also known as LY2062430) is also expected in the very near future. Amyloid antibodies are not all the same and whereas Bapineuzumab targets the N-terminal domain of the amyloid peptide, Sol recognizes the amino acids in the central region of the peptide (Aβ13-28). Moreover, Bapineuzumab binds more strongly to amyloid in plaques rather than soluble amyloid whereas Solanezumab preferentially binds to soluble amyloid-β. This distinction between antibodies can be detected clinically in so far as the fact that although Bapineuzumab produced ARIA-E, no such abnormalities were observed with Solanezumab (Farlow et al., 2012, Alz. Dementia, 8:261-271). Nevertheless, the expectations for Bapineuzumab and Solanezumab are not high. Hence, in June, the news agency Reuters reported that a survey of around 150 investors gave Bapineuzumab odds of about 5:1 for hitting its primary endpoints in the ApoE4 non-carrier Phase III studies whereas Solanezumab got the longer odds of 7:1. Although they may lack a deep scientific understanding of the underlying science, these investors nevertheless give a good indication of the expectations of the Wall Street community. Moreover, this expectation reflects the perception of Bapineuzumab and Solanezumab as being high risk, high reward assets. In other words, both antibodies have a low probability of success but if they do work, then they will justify their huge development costs not only in terms of market size but also, and more importantly, from the patient perspective.

The low expectations for Bapineuzumab and Solanezumab are related in part to the evidence emerging most notably from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) that suggests amyloid deposition occurs very early in the disease process and well before clinical signs appear (Jack et al., 2010, Lancet Neurol., 9:119-128) and that consequently amyloid-related therapeutics need to be targeted much earlier in the disease process (Karran et al., 2011, Nat. Rev. Drug Discov., 10:698-712).  In addition, the probably of success is further tempered by the difficulties inherent in the development of disease-modifying treatments for AD as highlighted by the recent Phase III failures of the Eli Lilly γ-secretase inhibitor Semagacestat (LY450139; Eli Lilly), which actually made cognition worse rather than better (plus it increased the risk of skin cancer), the Russian antihistamine latrepirdine (Dimebon or Dimebolin; Medivation/Pfizer), R-flurbiprofen (Tarenflurbil or Flurizan; Myriad Genetics/Lundbeck), for which Lundbeck signed a $350 million deal barely a month before the clinical data were released and finally homotaurine (Alzhemed or tramiprosate; Neurochem).

Irrespective of the outcome of the Bapineuzumab and Solanezumab trials, the US National Institutes of Health (NIH) announced in May that it will help sponsor the Alzheimer’s Prevention Initiative, which constitutes probably the most rigorous test of the amyloid cascade hypothesis in that it aims to prevent the development of AD in an at-risk population that show no signs of dementia.  This clinical trial, which is scheduled to commence in 2013, is being led by the Banner Alzheimer’s Institute in Phoenix, Arizona and plans to use the Genentech antibody Crenezumab (MABT; licensed from the Swiss company AC Immune) to treat pre-symptomatic members of an extended Colombian family living in and around Medellin. Within this family, there is a high incidence of early-onset AD which is caused by a mutation, E280A, in the presenilin 1 gene that is a part of the γ-secretase complex (Acosta-Baena et al., 2011, Lancet Neurol., 10:213-220). Family members with the mutation start to show cognitive impairment at around age 45 with full dementia developing by about age 51 (New York Times, 15 May, 2012). Crenezumab was chosen in part because it is an IgG4 antibody (Bapineuzumab and Solanezumab are IgG1) that activates microglia enough to help clear β-amyloid but not enough to produce the inflammatory signal that is thought to underlie some of the edema and microhemorrhages seen with other antibodies in clinical development (Adolfsson et al., 2012, J. Neuroscience, 32:9677–9689). The approximately $100 million trial will be funded by a mixture of philanthropic (Banner Institute), public (NIH) and private (Genentech) funding in a roughly $15:$16:$65 million split. This ground-breaking trial will be carried out on 300 hundred members of the 5000-strong Colombian family, with 100 carriers of the mutation receiving drug whereas a further 100 will receive a placebo and an additional 100 non-carriers will receive a placebo, with this latter arm being included since many family members do not want to know if they carrier the genetic mutation for the disease which is called locally La Bobera – the foolishness.

While the Alzheimer’s disease community awaits the outcome of the amyloid antibody Phase III studies with Bapineuzumab and Solanezumab, and despite the challenges in developing disease-modifying drugs for AD, a recent publication describes what could essentially be viewed as clinical proof-of-concept that amyloid lowering agents could be beneficial in the treatment of AD. Thus, Jonsson and colleagues (Jonsson et al., 2012, Nature, in press doi: 10.1038/nature11283) described a mutation in APP that protects against AD in the Icelandic population. Moreover, this mutation was adjacent to the BACE1 cleavage site of APP and in a cellular model, introduction of the mutation into APP resulted in an approximate reduction of 40% in the production of β-amyloid peptide relative to non-mutated APP. These data therefore support the strategy of BACE1 inhibitors as potential therapies for treating AD and imply that a BACE1 inhibition in the region of 40% may be sufficient. This publication is especially timely given the recent description at the Alzheimer’s Association International Conference held between 14-19th July in Vancouver, Canada, at which Eli Lilly, Merck and Eisai all described Phase I clinical data with BACE1 inhibitors (designated LY2886721, MK-8931 and E2609, respectively) (http://www.alzforum.org/new/detail.asp?id=3222). Hence, after more than a decade of struggle, during which time it was considered that it might not be possible to inhibit BACE1 with small molecules that were also brain penetrant and not substrates for P-glycoprotein (which pumps drug out of the brain), it would appear that significant progress is being made.

So, in summary, the recent announcement of the failure of Bapineuzumab to demonstrate any benefit in a Phase III study in ApoE4-positive AD is consistent with the Phase II data and is therefore not unexpected. The critical data in ApoE4 non-carriers should be available in early September. These data plus the additional Bapineuzumab Phase III studies as well as the soon-to-be-announced Phase III data with Solanezumab represent a key fork in the road of AD therapeutics. If the data are positive, then it is full steam ahead down the road to a regulatory filing and the eagerly awaiting AD patient population. If, however, these collective data are negative, the discussion will turn to whether the amyloid hypothesis has actually been tested early enough in the disease process or, alternatively, have side effects limited the doses of Bapineuzumab and Solanezumab to an extent that the clinical failures can be ascribed to shortcomings in  the antibodies themselves. If it is the latter, and given that all therapeutic antibodies are not equal, then this will encourage the further development of additional antibodies such as Gantenerumab (Roche), Ponezumab (Pfizer) and Crenezumab (Genentech) as well as encourage the further development of small molecular inhibitors of BACE1. If, on the other hand, the biomarkers included in the Bapineuzumab and Solanezumab clinical trials (amyloid imaging and CSF amyloid peptide measurements) give confidence that there are significant levels of target engagement, and that modulation of amyloid is not sufficient to produce clinical benefit in AD patients with established symptoms, then there will be a pause at the fork in the road. The AD research community will then have to ponder the signpost pointing down the difficult road towards earlier diagnosis or the equally difficult and poorly lit road towards alternative, non-amyloid (e.g. tau- or ApoE4-related) disease modifying approaches. But such decisions clearly need to be data-driven and so until all the Phase III results for Bapineuzumab and Solanezumab are available, it is prudent at this stage to just keep calm and carry on.