GlaxoSmithKline, Novartis, Roche, and Eli Lilly have joined forces to invest venture capital into Aileron Therapeutics, a biotech company based in Cambridge, MA that is using novel chemical structures to make a new class of medicines. GSK, Novartis, Roche and Lilly are all investing in a $40 million fundraising by the company.

Aileron’s synthetically locked (or “stapled”) peptides, in theory, will be able to target biochemical pathways involved in cell function and disease that conventional drugs cannot reach. Aileron plans to use the funding to pay for advancing the first experimental products towards clinical trials in 2010. Potential treatment areas include cancer, and immune, metabolic and infectious diseases.

“We believe that stapled peptides could represent a ‘fourth estate’ in therapeutics, emerging as a major class akin to small molecules, antibodies and vaccines,” said Michael Diem, partner at SR One, GSK’s venture arm.

Other investors in the latest funding round include Excel Medical Ventures and Apple Tree Partners. In previous financings, Aileron has raised $20 million in funding.