LONDON — British lawmakers voted on Friday in favor of a landmark bill that would for the first time help terminally ill adults end their lives.

The initial parliamentary vote in favor — 330 for and 275 against — starts months of debate and possible changes to the bill as it works through the House of Commons and the upper house of Parliament, the House of Lords.

If eventually passed, it will see the U.K. follow other countries such as Canada and Australia, as well as some U.S. states,…