A Study of the Safety and Tolerability in Participants With PIK3CA-related Overgrowth Spectrum or Proteus Syndrome Who Are Being Treated With Miransertib (MK-7075) in Other Studies (MK-7075-006)

This is a study of the safety and tolerability of oral miransertib (MK-7075) administered to participants at least 2 years of age with phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA)-related overgrowth spectrum (PROS) or Proteus Syndrome (PS). This is an extension of other miransertib studies (MK-7075-002 \[NCT03094832\] or ArQule CU/EAP \[NCT03317366\]), and may also enroll participants who are approved for MK-7075-002 but have not yet started miransertib therapy.

Inclusion Criteria: * Has PROS or PS and has been screened in Study MK-7075-002 (or has been approved by the Sponsor to screen for MK-7075-002) or is currently being treated with miransertib as part of Study MK-7075-002 (NCT03094832) or ArQule's CU/EAP (NCT03317366) * For males, agrees to be abstinent from heterosexual intercourse or use contraception unless confirmed to be azoospermic during the study period and for ≥90 days after the last dose of study intervention * For females, is not pregnant or breastfeeding, and is either not a participant of childbearing potential (POCBP) or is a POCBP and is abstinent or uses a highly effective method of contraception Exclusion Criteria: * Has previously discontinued miransertib due to related SAEs or other intolerance of miransertib * Has received other investigational agents, if any, that were administered between leaving Study MK-7075-02 or ArQule's CU/EAP and entering this trial * Is receiving systemic inhibitors of the mechanistic target of rapamycin (mTOR) pathway (eg, sirolimus, everolimus) * Is receiving immunosuppressive therapies * Is receiving continuous high dose steroids