The venture capital arms of GlaxoSmithKline, Novartis, Roche and Eli Lilly are investing in the US biotechnology company Aileron Therapeutics which is developing a novel class of drugs called stapled peptides.

Aileron, based in Massachusetts, has closed a $40 million series D financing, co-led by SR One, the independent corporate venture fund of GSK and Excel Medical Fund. The round also included Apple Tree Partners, the founding investor of Aileron, and the venture funds of Novartis, Lilly and Roche.

Proceeds from the financing will be used to advance Aileron’s lead stapled peptide programme toward clinical trials in 2010. Potential areas of interest include oncology, immune/inflammation, metabolic disease, and infectious disease.

Aileron noted that stapled peptides are synthetically locked, or 'stapled’, into an alpha-helical shape to create drug compounds that are uniquely effective for targets that are ‘undruggable’ with currently available approaches. In previous financings, Aileron has raised $20 million.

Michael Diem, partner at SR One, said “we believe that stapled peptides could represent a ‘fourth estate’ in therapeutics, emerging as a major class akin to small molecules, antibodies and vaccines”. Campbell Murray, managing director of Novartis Venture Funds, added that the progress to date of Aileron “has been very impressive, with a consistent flow of promising data showing the potential of stapled peptides”.

Aileron chief executive Joseph Yanchik said that the timing of the financing round “and the calibre of the participants is further validation of the growing belief in the transformative potential of this novel class of therapeutics”. He added that the interest highlights the need for “breakthrough technology platforms that will offer significant new growth avenues for the pharmaceutical industry”.

It is highly unusual for four pharma VCs to be involved in any given financing. In all of the 426 of biotech financing deals in 2008 and 2009, there are only four that included more than one such fund.