There is a 'small' trial that is equally or even more interesting than the ipilimumab + Nivolumab one from Bristol-Myers Squibb.
Similarly to that one, it involves two agents that target CTLA-4 and PD-1/PD-L-1. But it happens that these two agents are not from 'big' pharmas, so the trial is small. It's only available in Boston and New York.
The following trial is currently recruiting patients:
Phase I trial of tremelimumab (anti-CTLA-4) and MEDI4736 (anti-PD-L1) used in combination for patients with advanced solid tumors NCT01975831: http://clinicaltrials.gov/ct2/show/NCT01975831. This trial is sponsored jointly by the CRI/Ludwig Clinical Trials Network. Patients with advanced solid tumors, including colorectal cancer, are eligible for the trial.
So, the tremelimumab is similar to ipilimumab and MEDI4736 is similar to Roche/Genentech's MPDL3280A (as MPDL3280A, it targets PD-L1, the ligand, instead of nivolumab (anti-PD-1) that targets the protein)
The remarkable aspect is that Dr Wolchock is the study chair investigator and that it's sponsored by the leading institutions in immunotherapy for cancer:the Ludwig Institute for Cancer Research and the Cancer Research Institute.
It's probably less 'crowded', since it's a little difficult to choose, if you don't understand a bit more what's going on there ('just phase I', 'never heard of those drugs', 'it's not from a big company', etc.)
anti-CTLA-4 = anti-Cytotoxic T-Cell Lymphoma-4 Antigen