APM as a proxy for a client not supporting SPNEGO

Clarification:

Ipad IOS client (connected to SSL VPN) <---> APM <---> LTM <---> Websphere server

At the moment APM is not authenticating a client (no access policy applied to Vserver)

Client doesn't support spnego so only way to connect is to use login form. However same client can access sharepoint server in the same environment using NTLM. Is there any way in this scenario to allow client to connect to websphere backend without entering username / password? Would it be possible to enable authentication on APM and extract somehow client credentials and pass them to the back end? Any other options?

Thanks.