Nektar Therapeutics, a biopharmaceutical company, focuses on discovering and developing medicines in the field of immunotherapy in the United States and internationally. The company is developing rezpegaldesleukin, a cytokine Treg stimulant that is in phase 2 clinical trial for the treatment of systemic lupus erythematosus and ulcerative colitis, as well as phase 2b clinical trial to treat atopic dermatitis and psoriasis; and NKTR-255, an IL-15 receptor agonist, which is in phase 1 clinical trial to boost the immune system's natural ability to fight cancer. It has collaboration agreements with Takeda Pharmaceutical Company Ltd.; AstraZeneca AB; UCB Pharma S.A.; F. Hoffmann-La Roche Ltd; Bausch Health Companies Inc.; Pfizer Inc.; Amgen Inc.; UCB Pharma (Biogen); Bristol-Myers Squibb Company; Merck KGaA; and SFJ Pharmaceuticals, Inc. The company was incorporated in 1990 and is headquartered in San Francisco, California.