Potentially hazardous asteroid (PHA) 99942 Apophis, with a diameter 380-393 m (Licandro et al. 2016), came to its 2021 close approach on March 6, 2021, at 01:06 UT. It approached at 0.1126 au from Earth, providing an excellent opportunity to obtain good data to do a detailed study of its physical properties. The Solar System Group of the Instituto de Astrofísica de Canarias (IAC) participated in the International Asteroid Warning Network (IAWN) Observing campaign, an observational effort to better characterize Apophis. We did photometric, spectrophotometric and spectroscopic observations using several state-of-the-art telescopes in the Canary Islands observatories including the world largest optical telescope, the 10.4m Gran Telescopio Canarias (GTC). Observations started mid- January and will end mid-April. In this work we will present the observing program and some preliminary results.