Since July 2, 2012 it is now possible for third parties to submit observations during the international phase of PCT to the International Bureau. These observations can be made at any time after the publication of the international application and until the expiration of 28 months from the priority date and are limited to novelty and inventive step. They must be made by e-PCT system but may be published anonymously. They can be made in any language of publication of international applications, involve all or only part of the claims and should be based on more than 10 relevant documents, from which relevant passages must be indicated. The International Bureau verifies that these observations are relative to novelty and inventive step and transmits them to the applicant, international authorities and the public (via PATENSCOPE). The applicant has the right to respond until 30 months from the priority date either to the third party by e-PCT, or by mail to the International Bureau. This response is also available to international authorities and the public. After the expiration of 30 months from the priority date, the International Bureau will communicate these observations and comments of the applicant to designated Offices which have requested transmission.
See administrative instructions http://www.wipo.int/pct/en/texts/index.html and user’s guide: http://wipo.int/pct/en/epct/pdf/epct_observations.pdf