- Sergent, Petra;
- Pinto-Cárdenas, Juan;
- Carrillo, Adhara;
- Dávalos, Daniel;
- Pérez, Marisa;
- Lechuga, Dora;
- Alonso-Miguel, Daniel;
- Schaafsma, Evelien;
- Cuarenta, Abigail;
- Muñoz, Diana;
- Zarabanda, Yuliana;
- Palisoul, Scott;
- Lewis, Petra;
- Kolling, Fred;
- Affonso de Oliveira, Jessica;
- Steinmetz, Nicole;
- Rothstein, Jay;
- Lines, Louise;
- Noelle, Randolph;
- Fiering, Steven;
- Arias-Pulido, Hugo
Neoadjuvant intratumoral (IT) therapy could amplify the weak responses to checkpoint blockade therapy observed in breast cancer (BC). In this study, we administered neoadjuvant IT anti-canine PD-1 therapy (IT acPD-1) alone or combined with IT cowpea mosaic virus therapy (IT CPMV/acPD-1) to companion dogs diagnosed with canine mammary cancer (CMC), a spontaneous tumor resembling human BC. CMC patients treated weekly with acPD-1 (n = 3) or CPMV/acPD-1 (n = 3) for four weeks or with CPMV/acPD-1 (n = 3 patients not candidates for surgery) for up to 11 weeks did not experience immune-related adverse events. We found that acPD-1 and CPMV/acPD-1 injections resulted in tumor control and a reduction in injected tumors in all patients and in noninjected tumors located in the ipsilateral and contralateral mammary chains of treated dogs. In two metastatic CMC patients, CPMV/acPD-1 treatments resulted in the control and reduction of established lung metastases. CPMV/acPD-1 treatments were associated with altered gene expression related to TLR1-4 signaling and complement pathways. These novel therapies could be effective for CMC patients. Owing to the extensive similarities between CMC and human BC, IT CPMV combined with approved anti-PD-1 therapies could be a novel and effective immunotherapy to treat local BC and suppress metastatic BC.