After you send a pitch, an influencer has the opportunity to accept or decline it. They may decline your initial pitch but provide additional details and be open to negotiating.
You can cancel out a pitch by simply pitching the influencer again in the same campaign. For example, you could adjust the compensation amount, repitch and the new pitch will invalidate the previous one.
If you want to cancel a pitch completely and not move forward, you can click the archive icon in the top right corner. You can archive a pitch for any reason before it has been accepted by the influencer.