Acceleron Pharma Inc.

To start a Class Action lawsuit, please sign the Acceleron Pharma Inc. Retainer Agreement

This confirms that you have retained Monteverde & Associates PC to file an action with a complaint against Acceleron Pharma Inc. and/or its board of directors or officers. As a named plaintiff, you acknowledge that you owned shares in Acceleron Pharma Inc. prior to the recent takeover announcement and that you must maintain ownership in Acceleron Pharma Inc. throughout the litigation and/or closing of the transaction.

We agree to advance all expenses in the litigation, which means that you are not liable or responsible to pay any of the expenses of the action, whether attorneys’ fees or costs. Regardless of the result, we will never ask you to directly pay for any attorneys’ fees or costs. Should we obtain a favorable result, you authorize us to ask the court to award us compensation or seek reimbursement of expenses and up to one-third of any monetary class fund, or to negotiate and obtain a fee amount from defendants to be paid by the defendants, or its insurer or successor, but we will never ask you to pay any of the costs of this litigation.

As the client you are entitled to direct the litigation in any way you deem proper, and may at any time order us to dismiss the case or opt-out. Should you choose to do so, we will never ask you to reimburse us directly for any legal fees or expenses. During the course of this litigation, you authorize us to employ, share work and/or fees with other attorneys or law firms to prosecute your case.

We look forward to representing you in this case.

Sincerely,

Juan E. Monteverde, Esq.