The Torah says God will put enmity between the serpent and the woman's seed. Targum Pseudo-Jonathan on (Genesis 3:15) turns that enmity into a long, conditional war with an ending.
"When the sons of the woman keep the commandments of the law, they will be prepared to smite thee upon thy head; but when they forsake the commandments of the law, thou wilt be ready to wound them in their heel." The outcome of the battle depends on Torah. When Israel is faithful, the serpent loses. When Israel strays, the serpent gains.
And then the line that crowns the verse: "Nevertheless for them there shall be a medicine, but for thee there will be no medicine; and they shall make a remedy for the heel in the days of the King Meshiha."
The first messianic promise in the Torah
This is one of the earliest explicit messianic readings in all of rabbinic literature. The poison the serpent injects into humanity — mortality, sin, the struggle with the yetzer ha-ra — is not permanent. The days of King Messiah will bring the cure. The serpent gets no remedy. Humanity does.
The Targumist is writing redemption back into the curse. Before we even leave the garden, before Adam has taken a single step into the working world, God has already installed a fix.