.omega.-Halo-PGI.sub.2 analogues

A prostaglandin I.sub.2 analogue of the formula:

• ##STR28## wherein Y represents ethylene or trans-vinylene, R.sup.1 represents a hydrogen atom, a straight- or branched-chain alkyl group containing from 1 to 12 carbon atoms, an aralkyl group containing from 7 to 12 carbon atoms, a cycloalkyl group containing from 4 to 7 carbon atoms unsubstituted or substituted by at least one straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, a phenyl group unsubstituted or substituted by at least one chlorine atom, trifluoromethyl group, straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms or phenyl group, a --C.sub.m H.sub.2m COOR.sup.4 group, wherein m represents an integer of from 1 to 12 and R.sup.4 represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, a --C.sub.n H.sub.2n OR.sup.5 group, wherein n represents an integer of from 2 to 12 and R.sup.5 represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, or a ##STR29## wherein n is as hereinbefore defined and R.sup.6 and R.sup.7, which may be the same or different, each represent a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, R.sup.2 represents a hydrogen atom or a methyl or ethyl group, X represents a straight or branched chain --C.sub.p H.sub.2p -- group, wherein p represents an integer of from 2 to 8, or a ##STR30## wherein R.sup.8 represents a single bond, or a straight- or branched-chain alkylene group containing from 1 to 4 carbon atoms, R.sup.9 represents a single bond or a straight- or branched-chain alkylene group containing from 1 to 8 carbon atoms, and q represents an integer of from 3 to 6, R.sup.3 represents a chlorine or fluorine atom, the wavy line attached to the carbon atoms in positions 11 and 15 represents .alpha.- or .beta.-configuration or mixtures thereof, and the double bond between C.sub.5 -C.sub.6 is in the Z configuration, cyclodextrin clathrates thereof, and, when R.sup.1 represents a hydrogen atom, non-toxic salts thereof and, when R.sup.1 represents a ##STR31## in which n, R.sup.6 and R.sup.7 are as hereinbefore defined, non-toxic acid addition salts thereof.