正则表达式删除完整的HTML实体

We have a requirement to remove special characters from text strings. For example, we may get a string that looks like this; the ® is the registered trademark symbol:

PEPSI&#174; Bottle 20 oz<br><br>

I'm not great with regex, and can't figure out how to edit the existing code to produce that.

Here's what we currently have:

$ui = "PEPSI Bottle 20 oz<br><br>";
$ui = preg_replace('/[^A-Za-z0-9\.\' -]/', '', $ui);

This results in PEPSI174 Bottle 20 ozbrbr.

Our desired result is PEPSI Bottle 20 oz<br><br>.

How can I edit the regex to make sure that

1. It doesn't remove valid HTML tags like <br>, and
2. If it does find a special character entity, it removes not only the special characters (the & and #), but also the numbers and semicolon?

We don't want to have it remove all the numbers, as obviously the string can contain numbers; it's only numbers that are part of the entity code that we need to remove.

You could use this but now I can't guaranty it covers all the possible HTML entities:

$res = preg_replace('/&[A-Za-z0-9#]+;/', '', $ui);

That says replace any substring that: - starts with & - followed by any number of alphanumeric characters or # in random order - followed by ;.