I'm querying a mystery/thriller MS and I'm having trouble finding comps because my real comp is The Da Vinci Code. I bet you just cringed. But the truth is that I was inspired to write my MS after reading Da Vinci Code.
Specifically, I loved the chase through Vatican City, Rome, and the surrounding countryside. I loved solving the clues and exploring the merits of a conspiracy theory. I wanted to mirror these same aspects in my MS. So I found a different conspiracy theory and spent several years researching it. I've made up my own math and science clues and run them past multiple co-workers who hold PhDs in math. I set my story in a foreign country and traveled there myself as well as spent days researching satellite maps and interviewing people from that country.
Knowing we aren't supposed to compare our work to a bestseller like Da Vinci Code or Twilight or Harry Potter, I searched high and low for a different comp. I've spent days on Goodreads creating shelves and looking for recommendations that are similar to Da Vinci Code. I've gone through half a dozen library sites where librarians suggest books similar to Da Vinci Code. I've ordered and read books that seem like a promising comparable because it was a thriller set in modern-day with realistic historic/scientific clues to solve, but inevitably find the book is derivative of other Templar/religious conspiracies (my MS's conspiracy is neither) and/or the quality is just not as good as Da Vinci Code.
So for the sake of having a newer, not-as-popular comp, do I compare my work to a substandard derivative? I've sent out a dozen queries that uses the Da Vinci Code comp, and gotten 6 rejections within a week. I'm afraid agents are writing off my query as soon as they get to that comp.
Your problem isn't that your comp title is The DaVinci Code. It's that your book sounds like a knockoff of one of the biggest bestsellers of all time from TEN YEARS AGO. Agents were looking for DVC knockoffs in 2002, when the publisher was inundating the world with advance reading copies of DVC and everyone knew it was going to be huge.
Two years ago everyone wanted the next 50 Shades of Gray.
Two years from now everyone will want the next Patrick Lee. (I devoutly hope!)
In other words:The DaVinci Code ship has sailed and you will never row fast enough to keep up.
The good news for you though is that you are no longer limited to the narrow visioned agents and editors who want the Next Big Thing. You can publish this on your own, find an audience and make us all look shortsighted.
Or you can write your next book, pop this one in your steamer trunk for later when you're a famous writer and your publisher will be glad to publish it.