static void Main(string[] args)
{
  var invalidItemName = "<strong>This  is    a possible---item Name!<sup>™</sup></strong>";
  var notEntirelyFixed =
    Regex.Replace(invalidItemName, @"[^0-9a-zA-Z]+", " ").Trim();

  Console.WriteLine(notEntirelyFixed);
  Console.ReadKey();
}

// Result: strong This is a possible item Name sup sup strong