"As we have said previously, Valeant's board of directors has formed an ad hoc committee to review allegations related to the company's business relationship with Philidor and related matters."
Cummings' letter came just a few days after Reuters reported about how several top Valeant employees worked closely with the founders of Philidor to set up the business and expand its operations.
Two Valeant employees, for instance, were copied on a November 2014 email which contained an attachment explaining how Philidor employees could bill the highest amount an insurance company was willing to pay by resubmitting rejected claims at different price points.
The email, reviewed by Reuters, was sent to Tanner and Patel, who both used pseudonyms for their communications within Philidor. Reuters also reported that Pritchett was involved in building relationships with specialty pharmacies.
Valeant first disclosed its ties to Philidor late last month, amid concerns over the pharmacy's tactics to get insurers to pay for Valeant medications. It has since severed ties with the pharmacy, saying it has "lost confidence" in Philidor after questions about its business practices.
Committee spokeswoman MJ Henshaw said the panel is still in fact-finding mode and "at this point we don't feel that a subpoena is a necessary step that needs to be taken."
Valeant is also facing investigations by prosecutors in New York and Massachusetts over its drug pricing and programs that provide financial assistance to help patients cover out-of-pocket expenses for their medications.