The Cross-Border Biotech Blog

Biotechnology, Health and Business in Canada, the United States and Worldwide

Monthly Archives: July 2011

Friday Science Review: July 29, 2011

TK/GCV Suicide Gene Therapy: Connecting the Dots

Laval University ♦ Published in Cancer Gene Therapy (npg), July 22, 2011

Glioblastoma is an aggressive form of brain cancer requiring intensive therapy. Even with surgery, chemotherapy, and radiation, the mean survival time is approximately one year. A new therapeutic paradigm is currently being investigated in clinical trials, wherein a lentivirus delivers the herpes simplex virus thymidine kinase (TK) gene to the tumour bed following surgery. Tumour cells that are infected with the TK gene produce the TK protein, which in turn sensitizes tumour cells to the chemotherapeutic ganciclovir. After ganciclovir enters tumour cells it is phosphorylated by TK and then broken down into various toxic compounds that lead to cell death. In a nutshell the cell is altered genetically such that it commits suicide in the presence of the chemotherapeutic. One aspect critical to the success of this approach, however, is the degree to which tumour cells are connected; the therapy relies on something known as the “bystander effect”.

Researchers at the University of Laval have recently completed a comprehensive investigation on gap junctions in human glioblastomas. Gap junctions form between cells to allow intercellular communication through the migration of small molecules and peptides. They can be leveraged, therapeutically speaking, to amplify the efficiency of cancer therapies because they connect multiple cells into larger units. In the case of the suicide gene therapy described above, TK protein can migrate from cells that were successfully infected with the lentivirus into untransformed cells such that they are also eradicated in the presence of ganciclovir. In this study researchers found that connexin 43 (Cx43), the unit that assembles to form gap junctions in astrocytes, has heterogenous expression across glioblastoma cell lines. Analysis of 74 glioblastoma cell lines shows that Cx43 expression can be unaltered, reduced, or lost entirely. Cx43 expression was observed in 77% of cell lines, and its presence was adequate to provide a bystander effect regardless of whether its localization was considered normal or aberrant. Previous studies of smaller sets of glioblastoma cell lines had contradicting results, with some linking disease progression to loss of Cx43, while others supported the notion that high levels of Cx43 expression exacerbate disease conditions by promoting tumour cell infiltration into healthy tissue. This study provides the first comprehensive look at Cx43 in glioblastoma and should provide valuable information to companies in industry developing therapies that require a bystander effect for their success.

Structure of AMA1/RON2 Complex Elucidated

University of Victoria ♦ Published in Science, July 22, 2011

Apicomplexan parasites, including the Plasmodium species that cause malaria, have a very interesting mechanism that allows for host cell invasion. Upon contact with a host cell, these parasites release a structure known as a rhoptry neck (RON) complex that implants itself in the host cell membrane. A domain on RON2 then acts as a binding site for the apical membrane antigen 1 (AMA 1) displayed on the parasites cell surface. Essentially, apicomplexan parasites have evolved a means to provide both receptor and ligand to dock themselves on host cells. Once formed, the complex organizes itself into a structure known as a moving junction (MJ), a ring-like structure deeply embedded in the host cell membrane.  As this structure migrates from the anterior to the posterior of the parasite, the parasite becomes enveloped in a vacuole that is then internalized into the cell. Now researchers have elucidated the structure of the MJ complex at 1.95 angstrom resolution, providing valuable insight into its machinery. It is hoped that the structure can be used to develop therapies that prevent host cell invasion by apicomplexan parasites.

Monday Biotech Deal Review: July 25, 2011

Welcome to your Monday Biotech Deal Review for July 25, 2011.  Interesting tidbits from last week included the termination of the letter of intent relating to the proposed reverse-takeover transaction between Bradmer Pharmaceuticals and P1 Energy Corp., a distribution and marketing agreement between Valeant and Sanofi-aventis Canada, a $15M loan agreement between Protox Therapeutics and Oxford Finance LLC, the filing of a preliminary short-form base shelf prospectus in the Canada and U.S. by YM BioSciences, the closing of a $7M financing round for gIcare Pharma Inc., and the acquisition by Paladin Labs of a significant number of common shares of Afexa Life Sciences.  Read on to learn more.  Read more of this post

Friday Science Review: July 22, 2011

Genetic Basis for Gray Platelet Syndrome

Hospital for Sick Children ♦ University of Toronto ♦ University of Colorado ♦ University of Utah ♦ Others..

Published in Nature Genetics, July 17, 2011

Researchers have found a mutation in the gene NBEAL2 which seems to be at the root of Gray Platelet Syndrome (GPS), a disorder characterized by thrombocytopenia and enlarged platelets that lack α-granules. The discovery was enabled by RNA sequence analysis of platelets taken from an individual with autosomal recessive GPS. The mutation prevents recognition of a splice site at exon 9 in the mRNA strand encoding the protein neurobeachin-2. As a result of intron retention, premature stop codons are introduced to the mRNA strand; stop codons are known to cause mRNA degradation or protein truncation. Neurobeachin-2 contains a BEACH domain that is thought to be involved in cellular trafficking, and a defect in this protein likely leads to the manifestation of GPS.

Cell Fate Potential is Primed by Histones

McMaster University ♦ Published in Cell Stem Cell, July 8, 2011

Mick Bhatia’s lab has dug a little deeper into the mechanisms that bias lineage specification and differentiation of human embryonic stem cells (hESCs). Historically, it has been assumed that human embryonic stem cells are “equipotent”, meaning each and every one has the same potential, or equal potential, to differentiate into any of the more than 225 cell types in the human body. This theory has evolved over the last few years, and these recent findings confirm that the scene is quite a bit more colourful than originally thought. Embryonic stem cells are in fact restricted to certain lineages and this restriction is encoded by histone modification and patterning. Researchers in Bhatia’s lab illustrate this by fractionating stem cells in culture based on two surface markers, c-KIT and A2B5, and predicting cell fate based on histone modification marks observed on gene loci associated with pluripotency or various lineages.

Sorting with CD49f Provides Highest Reported Purity of HSCs

Campbell Family Institute for Cancer Research ♦ Ontario Cancer Institute ♦ University of Toronto

Published in Science ♦ July 8, 2011

Purification of specific cell types is essential to their study in vitro. Hematopoietic stem cells (HSCs), rare and quiescent cells that gives birth to all blood and immune cells in the bone marrow compartment, are under investigation for use in cell therapies and other regenerative medicine applications. Although fractions of cells can be enriched containing HSCs, all too often these subsets contain contaminating cell types that are not true stem cells. Lineage-restricted multipotent progenitors, for example, express the surface marker CD34, similar to HSCs, but do not exhibit the long-term multilineage graft potential that is indicative of a more primordial cell. Multiple markers have been analyzed at once in attempts to enrich solely for HSCs, but even these combinations, including CD38, Thy1, and CD45RA, are not adequate to do the trick. Researchers in John Dick’s lab have discovered a marker, CD45f, that seems to provide an even finer resolution while sorting for HSCs. Using flourescence-activated cell sorting, researchers enriched for a CD45f fraction and transplanted single cells into the femurs of mice. Many of these transplanted cells were capable of long-term multilineage engraftment. Sorting with CD45f allows for the highest purity of HSCs ever reported in the literature, coming in at around 9.5%.

Valuation and Other Biotech Mysteries – Part 8: The Current State of Healthcare Venture Capital

[Ed. This is the eighth part in Wayne's series. You can access the whole thing by clicking here. Please leave comments or questions on the blog and Wayne will address them in future posts in this series.]

The world of healthcare VCs has changed dramatically in the two decades which I have spent in capital markets. VCs are impacted by changes in the broader capital markets, changes in healthcare capital markets and changes in the industries on which they focus. Read more of this post

Valuation and Other Biotech Mysteries – Part 7: Funding the Cost of Developing a New Drug

[Ed. This is the seventh part in Wayne's series. You can access the whole thing by clicking here. Please leave comments or questions on the blog and Wayne will address them in future posts in this series.]

Assuming that the average direct cost of developing a new drug through regulatory approval will be at least $200 million, how and where do small companies get that funding? While these companies should access all potential sources of funding including government agencies and disease associations, the major sources of funding will likely be capital markets and pharma partners. Read more of this post

Monday Biotech Deal Review

Welcome to your Monday Biotech Deal Review for July 18, 2011.  Of note over the past week was the completion of Trimel’s qualifying transaction under the TSX-V’s capital pool company regime, resulting in Trimel’s expected re-listing on the TSX.  Also noteworthy was Valeant’s buying spree in the dermatology sector, with the purchase of dermatology assets from both Janssen Pharmaceuticals and Sanofi.  Read on to learn more. Read more of this post

Friday Science Review: July 15, 2011

New Target for AML

British Columbia Cancer Agency ♦ University of British Columbia ♦ Hannover Medical School ♦ Stanford University School of Medicine

Published in Cancer Cell, July 12, 2011

The MN1 locus is implicated in the development of acute myeloid leukemia (AML), where its up-regulation is a poor prognostic marker. Not all progenitors are transformed by MN1 over-expression though; common myeloid progenitors, rather than granulocyte-macrophage progenitors, are susceptible. In this study, researchers began to elucidate the genetic programs that underlie susceptibility to MN1 transformation. Complementation studies showed that MN1 required the MEIS1/AbdB-like HOX-protein complex to drive transformation. Chromatin immuno-precipitation illustrates that MN1 and MEIS1 have many identical chromatin targets, suggesting the two work together in some fashion to promote AML. Although MN1 relies on MEIS1 for transformation, it cannot activate expression of the complex, so transcriptional repression of MEIS1 could be an effective treatment paradigm for MN1-induced AML down the line.

De Novo Mutations in Non-Familial Schizophrenia

University of Montreal ♦ McGill University ♦ University of Hong Kong ♦ Others..

Published in Nature Genetics, July 10, 2011

In an eloquent study, researchers have identified a group of genes that could be responsible in part for the development of schizophrenia. The study involved 14 ‘trios’, including 14 schizophrenia patients and their parents. By focusing on non-familial cases (none of the patients had first- or second- degree family history of psychotic disorders), it could be assumed that the primary genetic events driving pathogenesis were the de novo mutations (DNMs)  occurring in the genomes of the patients themselves. The exomes of the 14 patients were sequenced which led to the identification of 15 DNMs in 8 of the patients, a much greater rate than previously reported. These findings suggest DNMs may contribute to the heritability of the disease and provide a list of targets for future consideration.

Mechanism of Carvedilol Elucidated

University of Calgary ♦ Rush University ♦ University of Iowa ♦ Thomas Jefferson University ♦ UC San Diego ♦ Others..

Published in Nature Medicine, July 10, 2011

One of the most potent beta blockers for the treatment of heart failure is carvedilol, however until now its mechanism of action was largely unknown. Researchers show that the small molecule suppresses a process known as store overload-induced calcium release (SOICR). When patients have tachyarryhythmias leading to heart failure, SOICR is usually the cause, and carvedilol was the only beta blocker under investigation that could suppress this calcium release. Carvedilol exerts its effects by reducing the period of time that cardiac ryanodine receptors are open for, and hence the amount of calcium that is released, preventing arrhythmia. To further investigate carvedilol’s SOICR-suppressing capabilities, researchers constructed an analog with vastly reduced beta blocking capacity and showed that it prevented stress induced ventricular tachyarrhythmias in mice. Combining the analog with selective beta blockers, like metoprolol or bisoprolol, produced optimal effects.

Using DNA to Program Quantum Dot Self-Assembly

University of Toronto ♦ Published in Nature Nanotechnology, July 10, 2011

Shana Kelley’s lab has impressed once again with this paper that illustrates how DNA can be used to not only guide the self-assembly of quantum dots, but regulate a series of properties that are crucial to their function in areas such as optical detection, solar energy harvesting, and biological research. Ideally quantum dots exhibit high luminescence efficiency, spectral tunability, control over valency (how many quantum dots a single dot is connected with), and bonding control. In this study, researchers constructed nanocrystals from cadmium telluride and capped them with specific sequences of DNA. The strategy for developing these ideal dots involved varying the brightness of dots, size of dots, the number of DNA strands per dot, and the sequences of those DNA strands. Combining these elements allows for broader functionality and a myriad of different construction possibilities, including cross-shaped forms containing three different dots. Although DNA-functionalized quantum dots have been made before, this is the first time they have been constructed with control over valency and other properties. Quantum dots can be switched on and off as well; modulating pH can alter conformation and the transfer of energy between dots in higher-order complexes.

Monday Biotech Deal Review: July 11, 2011

Welcome to your Monday Biotech Deal Review for July 11, 2011.  This week is a double feature, owing to last week’s break due to both Canada Day and Fourth of July holidays.  There was a lot of activity over the past two weeks in the biotech space.   Read on to catch up!  Read more of this post

Friday Science Review: July 8, 2011

Reductive DNA Damage, A New Evil

University of Waterloo ♦ University Health Network ♦ University of Toronto ♦ Published in PNAS, July 5, 2011

The mechanism behind oxidative DNA damage is well known. It has long been thought that oxidative damage causes the majority of DNA damage in a cell, leading to malignant transformation and cancer. New findings suggest that reductive damage is just as bad, if not worse, for the well-being of a cell. Scientists were able to observe ultrafast-electron-transfer reactions between a rare species of electron, known as a prehydrated electron, and different electron scavengers. These measurements are extraordinarily fast, occurring on the femtosecond time scale. When comparing the reductive damage done by electron transfer reactions involving prehydrated electrons, to the oxidative damage done by OH radicals, researchers came upon a rather surprising finding: the yield of reductive DNA strand breaks was roughly twice that of oxidative strand breaks, as measured using gel electrophoresis.

Clinical Study Results: Glutamic Acid Decarboxylase Vaccine in Patients with Type 1 Diabetes

Hospital for Sick Children (and other sites) ♦ Published in Lancet, June 27, 2011

Results from a clinical study run at multiple test centres in both Canada and the USA, indicate that an antigen vaccination targeting glutamic acid decarboxylase (GAD) was unsuccessful in treating type 1 diabetes. Although GAD is a major target of autoimmune response, preclinical data acquired through animal studies failed to translate into an effective treatment in the clinic. The patient group under examination included those 3 – 45 years of age, diagnosed with type 1 diabetes within 100 days. Patients received one of three courses of treatment: (1) three injections of GAD mixed with an adjuvant, (2) two injections of GAD mixed with adjuvant, and one injection of adjuvant alone, or (3) three injections of adjuvant alone.

The primary outcome of the study was the mean area under the curve of serum C-peptide during the first two hours of a meal tolerance test at one year. Patients in the group receiving three doses of the vaccine had a C-peptide value of 0.412 nmol/L at the one year mark, while those receiving three doses of the adjuvant alone had a value of 0.413 nmol/L; the loss of insulin secretion virtually unchanged.

Utilizing the host immune system to attack disease endogenously is a powerful paradigm upon which to build future therapies, but as is so often the case, finding relevant and predictive animal models is a serious limitation in their pursuit.

Valuation and other biotech mysteries – Part 6: The cost of developing a new drug

[Ed. This is the sixth part in Wayne's series. You can access the whole thing by clicking here. Please leave comments or questions on the blog and Wayne will address them in future posts in this series.]

The Tufts Center for the Study of Drug Development has been the source of the most comprehensive studies of new drug developments, including costs, success rates and strategies. Their estimates include the cost of the failures and the lost income from simply investing in government bonds. Neither of these factors is relevant to our current discussion although the former is critical to the success of the industry.

The clinical development pathways for both Theratechnologies Inc. (TSX:TH) (NASDAQ: THER) and Oncolytics Biotech (TSX:ONC)(NASDAQ:ONCY) have been outlined in previous parts of this blog series  and it is appropriate to look at the expenses for these companies. The expenses of Cardiome Pharma Corp. (NASDAQ: CRME) (TSX: COM) in their development of both intravenous and oral forms of vernakalant are also shown below. The information for all three companies was found from their annual financial statements at www.sedar.com in about 30 minutes.

Read more of this post

Friday Science Review: July 1, 2011

Cell Signaling Through the Eyes of an Adapter Protein

Mount Sinai Hospital ♦ University of Toronto ♦ Published in Nature Biotechnology, June 26, 2011

A novel approach to analyzing the protein machinery in cells utilizes affinity purification (AP) to identify protein-protein interactions, and a unique form of mass spectrometry, known as selected reaction monitoring (SLR), to identify novel proteins and quantify the kinetics behind the formation and disappearance of protein networks. To link the cell’s external environment with intracellular signaling, researchers focused on a transmembrane adapter protein, GRB2, which is at the core of an extraordinarily diverse group of protein interactions that are essential for cellular function.

GRB2 is a player in many tyrosine kinase receptor (RTK) pathways, so researchers hypothesized that by capturing it with affinity purification they would also capture a number of proteins involved in RTK signaling. To test their hypothesis they engineered a HEK239T cell line to express a FLAG-tagged version of GRB2 that would allow for purification of the adapter protein and any associated proteins. In order to broadly identify proteins in the RTK network that associate with GRB2, researchers treated 293 cells with the phosphatase inhibitor pervanadate and then purified GRB2 out of cell lysates with liquid chromatography.

Analysis of protein clusters allowed for the construction of a protein network with GRB2 at its hub. Further investigation allowed researchers to determine how this network fluctuates temporally in response to stimulation. By exposing 293 cells to epidermal growth factor for different periods of time, researchers used AP-SLR to create a dynamic version of the protein network illustrating changes in protein involvement over time.

GABA Exerts Dual Effects on Diabetic Condition

St. Michael’s Hospital ♦ University of Toronto ♦ Published in PNAS, June 27, 2011

Diabetes is an autoimmune disease characterized by the progressive loss of insulin-producing β-cells in the pancreas. The research community is investigating endogenous growth factors as a means to encourage the proliferation of β-cells in vivo. This approach does not remedy the underlying problem, however, as the body’s immune cells will continue to attack β-cells, exacerbating the disease. New findings provide evidence that suggests the central nervous system neurotransmitter GABA can play a dual role in treating the diabetic condition as it stimulates the proliferation of β-cells while suppressing their immune-mediated destruction.

Contrary to its function in the brain, GABA causes membrane depolarization, calcium-influx, and the activation of Pl3-K/Akt-dependent growth and survival pathways in the pancreas. Researchers found that GABA therapy can increase β-cell mass in vivo, and can actually reverse the disease in severely diabetic mice.  Interestingly, GABA also seems to suppress the cytokine storms that cause systemic inflammation and pancreatic infiltration by T lymphocytes and macrophages.

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