DESTINY-Breast03 was a phase three clinical trial comparing T-DXd to T-DM1 in a group of patients who all had HER2-positive metastatic breast cancer previously treated with Trastuzumab and Taxane. The initial reporting of these results was in 2021 and demonstrated a highly statistically significant improvement in median progression-free survival with T-DXd versus T-DM1. The median PFS hadn't yet been reached with T-DXd at the time, and with T-DM1 was 6.8 months, and those data were really immediately practice changing. We began to use T-DXd as standard of care in the second line setting. What was lacking at that time was maturity of the overall survival results. And so at San Antonio, we updated the overall survival results and we also updated the median progression-free survival results for this study. The overall survival was statistically significantly better with T-DXd at our reporting with a hazard ratio of 0.64.
Although neither arm had met a median overall survival at this time, this finding was statistically significant, reducing the risk of death by 36%, which solidifies the placement of T-DXd into the standard of care after Trastuzumab and Taxane. Our reporting of the updated survival results not only indicate a significant benefit in terms of survival, but we also were able to update our progression-free survival results, showing that T-DXd was associated with the median PFS of almost 30 months, whereas T-DM1 was around 6.8 months still. This is about four times greater median PFS with T-DXd compared to T-DM1, and so this longer follow up is allowing us to see just how durable these responses are in patients who are being treated with T-DXd. In addition, the objective response rate was around 78.5% with T-DXd, 21% of patients achieved a complete response, which is one in five patients treated had a complete response in a heavily pretreated diseased population.
So I think the results do continue to confirm the benefits of this agent with longer follow up. The updated safety results reported at San Antonio indicate the safety profile of T-DXd is consistent with what's been previously reported. From a clinical standpoint, I think it's important for us to watch for nausea and vomiting, which is common with T-DXd, so patients should be proactively treated to prevent it and then followed very closely to manage it and mitigate that side effect. Patients should also be warned about a higher rate of alopecia than you see with T-DM1. In terms of more serious adverse events of special interest, ILD was also monitored very closely on this study. We saw about 15% of patients develop all grade ILD on this trial, which was a bit higher than the 10% or so that we reported about a year ago.
This increased rate was due to a higher rate of Grade 1 or 2 or new Grade 1 or 2 events being reported in the last year, but no new Grade 3 events and still no Grade 4 or 5 events. So I think we're catching the ILD early and that is leading to our ability to avoid serious toxicity in terms of ILD. We are now as standard of care using T-DXd earlier, we're using it in the second line setting. Moreover, there is a study ongoing to see whether we can replace standard of care first line therapy, THP with T-DXd, which makes us wonder what are we going to use after T-DXd. And I think this is an area that's really important for us to research. We need data to tell us how well does T-DM1 work after T-DXd, how well does Tucatinib work after T-DXd? Because Tucatinib-based therapy from HER2 climb was conducted in a patient population that hadn't received T-DXd. So I don't think we have those data yet, but they are forthcoming and we'll have to pay special attention.
