e13024 Background: Hertraz, the first trastuzumab biosimilar was approved in Morocco in 2017. Real world data on trastuzumab biosimilars are very limited or not available. HERLife is a prospective, non-interventional phase IV study program that investigated the experience of using Hertraz, a biosimilar for trastuzumab (Herceptin), under routine clinical practice conditions in Morocco. The primary aim of this study was to confirm the acceptable safety and tolerability of Hertraz. Methods: Ninety-nine patients with HER2-positive breast cancer treated with Hertraz were enrolled from 8 public and private sector hospitals and followed up for 12 months as part of this non-interventional study. Cardiac events (LVEF) and other unexpected or serious adverse events were monitored. The study arms consisted of patients with early breast cancer (Arm 1, n=70) and metastatic breast cancer (Arm 2, n=29) whose median age was 53 years in both groups. Results: Switching from Herceptin to Hertraz was observed in 45% of 29 MBC patients and 27% of 70 EBC patients. Switching was done at a median of 4th cycle. Pertuzumab was used in combination with Hertraz in 69% and 19% of patients in the metastatic and neoadjuvant settings, respectively. Two patients had a decline in LVEF. One patient treated with Hertraz alone and one patient treated with Hertraz and pertuzumab developed a decrease in LVEF requiring a three-week treatment discontinuation of Hertraz. Treatment of Hertraz was continued after 1 skipped cycle without occurrence of new side effects. No other trastuzumab related adverse events was observed. Four patients in the metastatic group and 2 patients in the early breast cancer arm had a relapse in the 12 months of clinical follow-up. Conclusions: The management of HER2+ breast cancer in Morocco follows the international recommendations. This is the first real world safety data of Hertraz from Morocco. The 12-month follow-up treatment with Hertraz showed an acceptable cardiac safety profile. In cases where there was a switch from Herceptin to Hertraz or Hertraz combined with pertuzumab, the safety profile was similar to that previously reported in other studies.