"The company has never, to my knowledge, explained why it...

"The company has never, to my knowledge, explained why it focussed on elderly heavily pretreated patients. There would have been a medical or financial reason for this"

All human studies require approval from institutional human ethics committees before being undertaken. Clinical trials for unproven cancer treatments would never get ethics approval to be performed in patients who had not already received and failed conventional treatments. It's not ethical to withold a known beneficial treatment, in the hope that a new, unknown treatment might yield better results, but may give worse or no benefit. Hence the first efficacy studies in people are always performed in heavily pretreated patients.

My guess is that whichever company eventually licenses (hopefully!) the rights to use the various DEP-chemotherapy drugs will then run a larger phase III trial in untreated or less treated patients, using the current phase II data in their ethics applications to justify the use of the DEP drug instead of the current therapy.