Summary of HELICOS BIOSCIENCES CORP

Item 1.01 Entry into a Material Definitive Agreement

On October 8, 2009, Helicos BioSciences Corporation ("Helicos" or the "Company") entered into a Fifth Amendment to Lease (the "Fifth Amendment") with RB Kendall Fee, LLC (the "Landlord"). The Fifth Amendment amends the Lease dated as of December 30, 2005, as amended, by and between Landlord's predecessor in interest and Helicos (the "Lease"), demising approximately 56,461 rentable square feet of space located at the Company's headquarters in One Kendall Square, Cambridge, Massachusetts. Helicos' leased facility consists of a global headquarters, research and development facility and manufacturing plant.

Pursuant to the Fifth Amendment, the term of the Lease with respect to approximately 27,298 square feet of the Company's facility will be extended at the current rent level until November 30, 2009 and thereafter may continue to be extended by Helicos on a month to month basis from December 1, 2009 until March 31, 2010. In addition, pursuant to the Fifth Amendment, the Company agreed to terminate its use of approximately 10,144 square feet of excess general and administrative space. The Company's current rent obligations with respect to this excess space will end on October 31, 2009.

As a result of the Fifth Amendment, and assuming Helicos fully extends its month to month option described in the preceding paragraph, the lease for the entire space at Helicos' Cambridge, Massachusetts facility comprising approximately 46,317 square feet, shall expire on March 31, 2010.

The foregoing description of the Fifth Amendment is subject to, and qualified in its entirety by, reference to the Fifth Amendment, a copy of which is included as Exhibit 10.1 to this report and is hereby incorporated by reference.