I'd suggest re-writing your query to avoid ORs whenever possible. Is this generated by an ORM or subject to change with filters selected in application or can you totally control it on DB side?
It may be hugely more performant to simply rewrite this as (almost) the same query twice UNION ALL'd together to separate the productalt1_.alt_pdt_dbky OR productalt1_.orgnl_pdt_dbky conditions.