If I understand what you're looking for, it's actually pretty easy. Use a "not" pattern to exclude BCD.
DECLARE @Text1 VARCHAR(8000);
SELECT @Text1 = 'ABNAGENDRACSURENDRADJITHENDRAXNARENDRABVEERNDARAXDRMNDRAXRVINDRABNAGENDRACSURENDRADJITHEN';
-- 111111111122222222222333333333444444444455555555556666666666777777777788888888889
-- 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
SELECT StringPart = SUBSTRING(@Text1, PATINDEX('%A[^BCD]NARENDR%',@Text1),9)
,StringPartLocation = PATINDEX('%A[^BCD]NARENDR%',@Text1);
--Jeff Moden
Change is inevitable... Change for the better is not.