The present invention relates to 5-thia-
omega-substituted phenylprostaglandin E derivatives of the formula (I)(wherein, all the symbols are as defined in the specification), process for producing them and pharmaceutical compositions comprising them as 
active ingredient.The compounds of the formula (I) can bind to PGE2 receptors (especially, subtype EP4) strongly, so they are expected to be useful for prevention and / or treatment of 
immunological diseases (autoimmune diseases such as 
amyotrophic lateral sclerosis (ALS), 
multiple sclerosis, Sjoegren'
s syndrome, chronic rheumarthrosis and 
systemic lupus erythematosus etc., and rejection after 
organ transplantation etc.), 
asthma, abnormal 
bone formation, neuronal 
cell death, 
lung failure, 
liver damage, 
acute hepatitis, 
nephritis, renal insufficiency, hypertension, myocardiac 
ischemia, 
systemic inflammatory response syndrome, ambustion pain, 
sepsis, hemophagous syndrome, macrophage activation syndrome, Still's 
disease, 
Kawasaki disease, burn, systemic granulomatosis, 
ulcerative colitis, Crohn's 
disease, hypercytokinemia at 
dialysis, multiple organ failure, and shock etc. Further, it is thought that EP4 subtype 
receptor relates to sleeping disorder and blood 
platelet aggregation, so the compounds of the present invention are expected to be useful for the prevention and / or treatment of such diseases.