Abstract
The NDA will be pursued under an accelerated approval pathway based on existing data. As part of its filing with the FDA, Prosensa said, it will commit to launching two confirmatory postapproval studies for drisapersen.
“Re-dosing protocols are in the process of being submitted to relevant Institutional Review Boards and we remain on track to re-dosing the first patients before the end of the quarter,” Prosensa said on August 12 in a statement (Prosensa, 2014).
One of the planned confirmatory studies may use as a control group the 269 boys aged 3–18 having confirmed DMD, with whom the company completed its enrollment in its natural history study back in June. The study's purpose is to characterize the natural history and progression of DMD in order to help inform the design of future studies, capture biomarkers of safety and disease progression, and provide comparative data for development of therapies for DMD involving rare exons, for which formal controlled trials are not feasible.
PRO044, a Prosensa experimental drug designed to address a separate subpopulation of up to 6% of DMD patients, may serve as the follow-up exon skipping compound in one of the two confirmatory studies toward supporting an accelerated approval for drisapersen. An extension study for PRO044 is on track to commence in the fourth quarter of this year, the company said, with a placebo-controlled study scheduled to begin in the first half of 2015.
Prosensa announced the updates along with its results for the second quarter. The company reported a net loss of €8 million ($10.5 million) compared with a €4.7 million (about $6.2 million) net loss in Q2 2013. Quarterly revenue dropped to zero from €2 million ($2.6 million), with Prosensa citing a decrease in license revenue of €1.3 million ($1.7 million), and a drop in collaboration revenue of €0.7 million ($919,700) because of the termination of its research and collaboration agreement with GlaxoSmithKline in January 2014.
A day earlier on August 11, Prosensa said it would use up to €5 million (about $6.6 million) from CureDuchenne to support the company and accelerate development of, and patient access to, DMD therapies. The funding is to be provided through convertible promissory notes.
Other development efforts in the works, according to Prosensa, include dose-finding studies for PRO045 and PRO053, experimental drugs each addressing a population of up to 8% of all DMD patients. The company said it expects data for PRO045 to emerge in the fourth quarter of this year, and for PRO053 in the first half of 2015, with additional studies of these compounds to begin in 2015.
InoCard's lead program is a gene therapy designed to express the calcium-binding protein S100A1, and set to start its first human trial in 2016. S100A1 has been shown by InoCard founders Prof. Patrick Most and Prof. Hugo Katus to be a master regulator of myocardial function, based on their discovery that S100A1 is downregulated in CHF.
According to the companies, administration of S100A1 has demonstrated in vivo beneficial effects on contractile force, growth control of heart muscle cells, and rhythm stability of the heart, while showing it is also able to adapt the heart's energy supply to increased cardiac output. In a porcine heart failure model, treatment with InoCard's gene therapy AAVS100A1 demonstrated a 12-month survival rate of 90%.
“There is strong scientific rationale that addressing calcium dysregulation leads to an astounding effect in congestive heart failure,” Jörn Aldag, uniQure's CEO, said on August 11 in a statement (uniQure and InoCard, 2014).
uniQure's lead product is Glybera® (alipogene tiparvovec), which is marketed in the European Union for a subset of patients with lipoprotein lipase deficiency, also known as LPLD or hyperchylomicronemia. Glybera is the first gene therapy approved by regulatory authorities in the Western world.
On February 5, uniQure began trading its first shares on the NASDAQ Global Select Market, raising a total $91.8 million by selling 5.4 million shares at an initial offering price of $17 per share. Profs. Most and Katus will join uniQure as, respectively, managing director of the company in Germany, and chairman of the company's Scientific Advisory Board for cardiovascular diseases.
uniQure agreed to pay InoCard shareholders €1.5 million ($1.97 million) in cash and an equivalent amount in stock, all of it upfront. uniQure also agreed to pay undisclosed amounts to InoCard toward success-based milestones and royalties.
RM is the coexistence of cells carrying disease-causing mutations with cells where the inherited mutation is genetically corrected by a spontaneous event. In seven unrelated patients with different DEB subtypes, RM corrected both null mutations, resulting in complete loss of collagen VII and severe disease, as well as missense or splice-site mutations associated with some preserved collagen VII function and a milder phenotype, according to a team of researchers from the Netherlands, Germany, and Spain.
Five of the seven DEB patients (71%) studied showed that their conditions were corrected through RM mechanisms that included back mutations and/or mitotic recombinations that resulted in the absence of a mutation on one allele. The remaining two DEB patients' conditions were corrected through second-site mutations that affect splicing, the team reported in a study published in Journal of Investigative Dermatology.
Anna M.G. Pasmooij, PhD, of University Medical Center Groningen (UMCG;
The mutation, subtype, and severity of the disease were shown not to be decisive factors in the presence of RM, which was found to have occurred in both autosomal dominantly and recessively inherited DEB. Evidence for reversion of DEB was found only in keratinocytes, even though collagen VII is synthesized and secreted by both keratinocytes and fibroblasts. The team suggested that isolated revertant keratinocytes could be cultured into skin grafts and used as an autologous skin transplant on affected skin or mucosal areas.
However, researchers also cautioned that isolation and culturing of the revertant cells must be optimized before large sheets of cells become available, and additionally suggested that another approach could use induced pluripotent stem cells, based on studies that have shown that mouse- and human-induced pluripotent stem cells can be differentiated into keratinocytes.
While those vectors can enter cells efficiently and deliver therapeutic DNA or RNA molecules without degradation, the process of rendering natural viruses harmless has proven difficult. For viruses to survive, a significant fraction of the replicated genomes have to be completely protected by coat proteins that interact with the nucleic acids. But the process is based on reversible, weak, and allosteric interactions. That has led to research into alternative “viruslike” vectors based on synthetic molecules. However, researchers have been unable to achieve the required precise packaging of individual DNA molecules with a protective coating of synthetic molecules.
Instead of synthetically coating individual DNA molecules, the researchers designed and produced artificial viral coat proteins using the natural machinery of yeast cells. When the proteins were mixed with DNA, they spontaneously formed “artificial viruses” with highly protective protein coats around each DNA molecule. The process was similar in many respects to that of the tobacco mosaic virus, which served as a model for the artificial virus.
In results published in Nature Nanotechnology, the researchers reported that the artificial viruses were as effective as current methods for delivering DNA to host cells based on synthetic molecules, since they allow for greater precision in packaging DNA molecules. The artificial viruses can also be developed for other applications in which viruses are now being used, in fields such as biotechnology and nanotechnology, the team added.
“Our virus-like particles protect DNA against enzymatic degradation and transfect cells with considerable efficiency, making them promising delivery vehicles,” the researchers concluded (Hernandez-Garcia et al., 2014). The study's corresponding authors were Armando Hernandez-Garcia, PhD, formerly of Wageningen University and now of Northwestern University (
While patients treated for blood cancers with human leukocyte antigen (HLA)-matched allogeneic stem cell transplants can generally reduce their risk and severity of graft versus host disease (GvHD), the disorder remains a significant cause of illness and death where HLA has been mismatched. Those risks are higher for patients with high-risk leukemia, who instead have a substantial risk of relapse early after transplantation—despite efforts to reduce GvHD likelihood by depleting donor T cells from the stem cell graft, and then readministering them into patients 6 months after transplantation.
In four cleanroom demonstrations, the LUMC researchers used Streptamer-based isolation technology to isolate pure populations of virus-specific T cells, followed by transduction with good manufacturing practice-grade cells encoding the minor histocompatibility antigen HA-1-TCR. The isolation and transduction resulted in rapid in vitro generation of highly pure, dual-specific engineered T cells that showed either comparable or greater effectiveness than the parental HA-1-specific T cell clone in antigen specifically recognizing HA-1+ malignant cells.
“Due to the short production procedure of only 10–14 days and the defined specificity of the T-cells, administration of virus-specific T-cells transduced with the HA-1-T-cell receptor as early as 8 weeks after allogeneic stem cell transplantation is feasible,” the research team concluded in its study, published in the journal Haematologica (van Loenen et al., 2014). The study's corresponding author was Marleen M. van Loenen of LUMC.
The LUMC study comes about a year after publication of a study into another method posited as a potential first step toward developing an autologous TCR gene therapy targeting patient-specific neoantigens in human cancer. In that study, researchers from the Netherlands joined colleagues from Denmark, Germany, Russia, and the United Kingdom in detailing their development of a high-throughput DNA-based strategy to identify TCR sequences from large numbers of samples by the capture and sequencing of genomic DNA fragments encoding the TCR genes.
Researchers assembled a library of tumor-reactive TCRs from patient material and various “nontolerant” sources. They then identified TCRαβ pairs in bulk antigen-specific T cell populations in either human material or from humanized mice. Finally, they assessed the TCR repertoire of intratumoral T cell subsets without knowledge of antigen specificity.
The researchers said TCR gene capture holds promise by allowing for description and re-creation of the library at sites of viral infection or autoimmune disease, and by allowing the creation of large collections of TCR genes for genetic engineering of T cell immunity. The method can be used to rapidly identify tumor-reactive TCR genes in a patient-specific manner, probably including TCR genes that are reactive to patient-specific neo-antigens.
“If such TCRs can also be rapidly re-introduced into autologous T-cells, preferably in conjunction with a suicide switch this would allow one to ‘transplant’ the tumor-reactive TCR repertoire from exhausted T-cells into a more fit T-cell population,” according to the study, published in Nature Medicine (Linnemann et al., 2013). Corresponding authors for the study were Ton N.M. Schumacher, PhD, of the Netherlands Cancer Institute (
Applying these nucleases together with donor DNA delivered as protein-capped adenoviral vector (AdV), free-ended integrase-defective lentiviral vector, or nonviral vector templates resulted in scarless, homology-directed genome editing for the vast majority of AdV-modified human cells. In addition, donor delivery by AdVs resulted in diminished off-target chromosomal insertion, concatemeric “footprint” formation, and prokaryotic DNA incorporation. As a result, genetically modified cell populations generated via AdV donor DNA transfer showed homogenous transgene activity, concluded the study, whose corresponding author was LUMC's Manuel A.F.V. Gonçalves, PhD.
By contrast, the researchers added, a significant proportion of cells exposed to free-ended or covalently closed HR substrates were subjected to random and illegitimate recombination events. “On the basis of our findings, we put forward the view that the numerous efforts devoted to minimizing off-target activity of sequence-specific nucleases should be complemented with those aiming at identifying HR [homologous recombination] substrates whose features maximize on-target and accurate insertion of foreign DNA,” the researchers concluded in their study, published in Nature Methods (Holkers et al., 2014).
Researchers added that the findings are particularly relevant for genome engineering approaches that aim at carrying out high-fidelity genetic modification of human cells. The study defined specificity as the relative frequencies of on-target versus off-target insertions, and accuracy as the structure or arrangement of site specifically integrated exogenous DNA.