Prosensa Raises $30M for Exon-Skipping Drug Pipeline

By Cormac Sheridan
BioWorld Today Correspondent

Prosensa Therapeutics BV raised €23 million (US$29.9 million) in a Series C round to enable it to move two new exon-skipping antisense oligonucleotide drugs into clinical development in Duchenne's muscular dystrophy (DMD) and to take forward preclinical programs in two other rare disease indications.

"The rare disease space is something that's got a lot of attention in the last few years. There's a strong interest in the VC community in rare diseases," Luc Dochez, Prosensa's chief business officer, told BioWorld Today.

In addition to growing its clinical pipeline of drugs for DMD, Prosensa, of Leiden, the Netherlands, also is taking forward programs in myotonic dystrophy type 1 (DM1) and Huntington's disease, both of which are trinucleotide repeat disorders characterized by the presence of greatly expanded repeat sequences that disrupt normal protein function.

DM1, an autosomal dominant condition that involves the presence of a CTG repeat in the gene encoding dystrophia-myotonica protein kinase, has an adult age of onset. It is characterized by progressive muscle loss and weakness and a wide array of other symptoms, depending on disease severity.

Huntington's, also an autosomal dominant condition, is caused by CAG repeats in the gene encoding the huntingtin protein and is associated with progressive loss of muscle coordination and cognitive function.

Combating each involves an alternative to the exon-skipping approach that Prosensa has pioneered. "It's a specific reduction of the triplet repeats," Dochez said. It still involves mRNA modulation using antisense oligonucleotides, however. "It's a selective, specific silencing approach."

The two programs, PRO0135 for DM1 and PRO289 for Huntington's, have entered preclinical development but are still two to three years from the clinic.

"The in vitro and in vivo results were very encouraging. Are we there yet? Absolutely not," Dochez said. However, the new cash – and, potentially, new partnerships – will help take the firm further.

In DMD, meanwhile, the company's lead drug candidate, PRO051 (GSK2402968), is undergoing a Phase III trial that began 12 months ago, as part of 2009's potential £428 million (US$669 million) DMD alliance with London-based GlaxoSmithKline plc. Several Phase II trials are under way as well, and data could start to flow as early as later this year. PRO051 addresses mutations in exon 51 of the gene encoding dystrophin, the large muscle protein involved in anchoring the cytoskeleton to the extracellular matrix. It addresses, potentially, 13 percent of the DMD population.

A second molecule, PRO044, for which GSK retains an exclusive option, is undergoing a Phase I/II trial. Two other molecules, PRO045 and PRO053, which are designed to skip exons 45 and 53 of the gene encoding dystrophin, respectively, will enter Phase I/II trials in DMD this year. Each addresses about 8 percent of the patient population.

GSK has an option to license one of those, while Prosensa will retain limited commercial rights in undisclosed territories. Prosensa will retain full rights on the second compound.

New Enterprise Associates, of Menlo Park, Calif., led the new round, which represents its first European biotech investment. Existing Prosensa investors Abingworth, Life Sciences Partners, Gimv, Idinvest Partners and MedSciences Capital also participated in the financing.

"It should take us well into 2014, excluding any milestones from the GSK collaboration," Dochez said. Some £27 million in development funding and milestones are on offer under the present phase of the alliance. (See BioWorld Today, Sep. 14, 2011.)

Prosensa last raised financing in December 2008, and has banked €54.5 million in investment since its formation in 2002. The company is plotting an independent course and has no ambitions to undergo an early exit via a trade sale.

"Our ambition is to become a rare-disease-focused specialty biotech company," Dochez said. "To enable that, a public financing at a certain point in time is certainly one of the options to consider."

That is an issue for another day, however. "I'm just smelling the roses for a second," he added. "I'll worry about that question tomorrow."

In other financings news:

• Generex Biotechnology Corp., of Worcester, Mass., said it secured two commitments to raise aggregate capital of C$3.6 million (US$3.56 million). The funding is structured as one-year term loans from private lenders, secured by the company's real estate. Interest on the loans is payable monthly at 10 percent annually. The company said the capital infusion would allow it to advance redevelopment plans without diluting the value of its stock. The first loan, for an aggregate of C$2.5 million, closed Jan. 19. The second loan is scheduled to close on or before Jan. 30.

• OncoSec Medical Inc., of San Diego, filed an S-1 registration with the SEC seeking to raise up to $10 million. At press time, the offering of common stock and warrants had not priced. Rodman & Renshaw LLC is serving as lead placement agent for the offering. The company is developing electrochemical and cytokine-based immune therapies to treat solid tumors via electroporation delivery. On Wednesday, the company's shares (OTCQB:ONCS) closed at 41 cents, up 1 cent. (See BioWorld Today, Aug. 12, 2011.)