Acute graft-versus-host disease (GVHDa) is one of the leading causes of morbidity and mortality after allogeneic hematopoietic stem cell transplant (HSCT) patients. While the first-line consensus treatment has been based on systemic corticosteroid therapy for many years, ruxolitinib has recently been approved and has become the standard second-line treatment. Nevertheless, the effectiveness of ruxolitinib remains limited to 40 % of cortico-resistant patients, raising the crucial question of selecting a third-line treatment. Among the therapeutic modalities described, this workshop selected fecal microbiota transplantation (FMT), mesenchymal stromal cells (MSC) injection, and extracorporeal photopheresis (ECP) as the most promising or with a benefit/risk balance that favors their prescription at this stage. The workshop also highlighted the importance of research aimed at identifying markers or score calculations that guide toward a risk-adapted approach as early as possible. To date, aside from calprotectin, no marker or score is routinely used, but all are the subject of intense research. Finally, measures associated with specific treatment remain crucial, and new developments in dietary contributions, infection prophylaxis, and tissue regeneration are also addressed.