DMD antisense oligonucleotide mediated exon skipping efficiency correlates with flanking intron retention time and target position within the exon.

Mutations in the DMD gene are causative for Duchenne muscular dystrophy (DMD). Antisense oligonucleotide (AON) mediated exon skipping to restore disrupted dystrophin reading frame is a therapeutic approach that allows production of a shorter but functional protein. As DMD causing mutations can affect most of the 79 exons encoding dystrophin, a wide variety of AONs are needed to treat the patient population. Design of AONs is largely guided by trial-and-error, and it is yet unclear what defines the skippability of an exon. Here, we use a library of phosphorodiamidate morpholino oligomer (PMOs) AONs of similar physical properties to test the skippability of a large number of DMD exons. The DMD transcript is non-sequentially spliced, meaning that certain introns are retained longer in the transcript than downstream introns. We tested whether the relative intron retention time has a significant effect on AON efficiency, and found that targeting an out-of-frame exon flanked at its 5'-end by an intron that is retained in the transcript longer ('slow' intron) leads to overall higher exon skipping efficiency than when the 5'-end flanking intron is 'fast'. Regardless of splicing speed of flanking introns, we find that positioning an AON closer to the 5'-end of the target exon leads to higher exon skipping efficiency opposed to targeting an exons 3'-end. The data enclosed herein can be of use to guide future target selection and preferential AON binding sites for both DMD and other disease amenable by exon skipping therapies.

Systemic Antisense Therapeutics for Dystrophin and Myostatin Exon Splice Modulation Improve Muscle Pathology of Adult mdx Mice.

Antisense-mediated exon skipping is a promising approach for the treatment of Duchenne muscular dystrophy (DMD), a rare life-threatening genetic disease due to dystrophin deficiency. Such an approach can restore the disrupted reading frame of dystrophin pre-mRNA, generating a truncated form of the protein. Alternatively, antisense therapy can be used to induce destructive exon skipping of myostatin pre-mRNA, knocking down myostatin expression to enhance muscle strength and reduce fibrosis. We have reported previously that intramuscular or intraperitoneal antisense administration inducing dual exon skipping of dystrophin and myostatin pre-mRNAs was beneficial in mdx mice, a mouse model of DMD, although therapeutic effects were muscle type restricted, possibly due to the delivery routes used. Here, following systemic intravascular antisense treatment, muscle strength and body activity of treated adult mdx mice increased to the levels of healthy controls. Importantly, hallmarks of muscular dystrophy were greatly improved in mice receiving the combined exon-skipping therapy, as compared to those receiving dystrophin antisense therapy alone. Our results support the translation of antisense therapy for dystrophin restoration and myostatin inhibition into the clinical setting for DMD.

A phase II trial of pemetrexed and gemcitabine as first line therapy for poor performance status and/or elderly patients with stage IIIB/IV non-small cell lung cancer.

Pemetrexed and gemcitabine are both active agents for the treatment of locally advanced or metastatic NSCLC. We tested a novel biweekly combination of pemetrexed and gemcitabine for tolerability and efficacy in 45 elderly and/or poor performance status patients (44% female, mean age of 72.4 years) with measurable stage IIIB/IV NSCLC. Patients received biweekly cycles of pemetrexed 500 mg/m(2) IV over 10 min followed by gemcitabine 1500 mg/m(2) IV with vitamin B12 1000 microg IM, and folic acid 1mg po daily beginning 7 days before and continuing throughout treatment (median of 4 cycles). Ten patients experienced grade 3/4 neutropenia, two had grade 3 febrile neutropenia, and two had grade 3 anemia. Patients with ECOG PS 2 appeared poorly suited for the regimen, with 61.5% completing < or = 2 cycles. The overall response rate was 17.8%, the clinical benefit rate (CR+PR+SD >24 weeks) was 26.7%, and the median progression free survival was 3.5 months. However, ECOG 0-1 patients had longer PFS and tended to have a better response rate than ECOG 2 patients.