Yes. This is offered by many carriers to protect fiduciaries who had a claims-made policy with a different carrier immediately prior to the current policy and who did not want to buy an Extended Reporting Period Endorsement when the old policy ended.
Prior Acts Coverage protects against claims arising out of activities that took place before the inception date of a new policy, but which result in claims during the policy. Let's say you purchased a claims-made policy from Company A, with an effective date of January 1, 2011. At the end of 2011, you move your coverage to Company B but you get Prior Acts coverage going back to you original January 2011 Retroactive Date. You are then sued in March 2012 (so the Claim is made in 2012) but arising out of alleged negligent work you did in 2011. You would be covered under the new policy, so long as the Prior Acts endorsement was in place. The new policy would respond to the claim and apply to provide a defense/indemnity. Carriers usually charge an additional premium for this coverage but it is often well worth it. It removes the chance of having a claim come in that falls “in between” the policy years and leaves you without coverage and facing a claim on your own.