I found this information:
Here’s what I found regarding the combination of doxorubicin (a chemotherapy agent) and Viagra (sildenafil) in the treatment of prostate cancer:
Scientific Basis & Preclinical Findings
1. Enhanced Cancer Cell Killing & Cardiac Protection
Lab studies and mouse models have shown that sildenafil (a PDE-5 inhibitor) enhances the effectiveness of doxorubicin against prostate cancer cells. This combo:
Boosts apoptosis (cell death) in PC-3 and DU145 cancer cells.
In mouse models, the combination significantly reduced tumor size while also protecting against the heart damage doxorubicin typically causes.
2. Mechanistic Insight—DNA Repair Disruption
Further research showed that sildenafil impairs the cellular DNA repair systems (both homologous recombination and non-homologous end joining). This makes doxorubicin-induced DNA damage more lethal to cancer cells.
3. CD95-Mediated Apoptosis
Another pathway involves modulation of CD95 (Fas receptor) and its inhibitor FLIP. Sildenafil plus doxorubicin reduces FLIP levels, enabling CD95 to drive more potent apoptosis in prostate cancer cells.
Clinical Evidence & Early Human Data
There is very limited human clinical trial data for this combination, but one randomized study did explore it:
Safety vs. Efficacy: In a clinical study examining doxorubicin with and without sildenafil, the combination was generally tolerated with mostly mild side effects (e.g., headache, flushing). However, a concerning decline in left ventricular ejection fraction (LVEF) occurred in one patient—but that individual was also on trastuzumab, making it unclear whether sildenafil was responsible. Ultimately, the trial continued, but found no evidence of cardiac protection from adding sildenafil.
Summary:
“There’s promising preclinical evidence showing that sildenafil can enhance doxorubicin’s cancer-killing effects—by impairing DNA repair pathways and promoting apoptosis—and even toggle some heart protection in animal models. However, in the limited human data available, sildenafil didn’t reduce heart damage and didn’t show treatment benefit. More clinical trials are needed before this combination can be considered for actual use.