MOND (or Modified Newtonian Dynamics) has been around for a long time. The problem is making the equations work. Newtonian physics has proved to be extremely accurate for every space mission we've deployed to date. So, it certainly scales to Solar System level.
I suspect the reason this is being discussed is because of the recent death of Vera Rubin; a personal heroine of mine. Her book, Bright Galaxies, Dark Matters, is wonderful for anyone remotely interested in dark matter. It's one of the very few paper books I retain. I just love owning it and reading bits of it from time to time.
Vera's hope was that it is Newtonian physics that is wrong, and that dark matter, as a sub-nuclear particle, is not the cause of the galactic gravitational anomaly. I'm with Vera on this.
It's disgraceful that she wasn't awarded a Nobel for her work, and I'm not the only one to think so: http://www.nytimes.com/2017/01/04/opinion/why-vera-rubin-deserved-a-nobel.html
Edit: So the non-relativistic component of MOND bothered me. I found this: https://arxiv.org/abs/1112.3960