Can you please spell out MOTS and COMB or provide a link to the reports? These are not acronyms I am familiar wit, and I would like to read them.
Sue

Thanks to @johnbishop, I found the information you referred to.
Always seeking more natural interventions for health and wellness, I read both with a great deal of curiosity. I am learning a lot! Enough to be encouraged that there may be answers on the horizon.

Here is my analysis of the MOTS (Melatonin-micronutrients Osteopenia Treatment) Study:
This was a well-designed and executed small study of a population having osteopenia, not osteoporosis, and no high cholesterol, high blood pressure, inflammatory/autoimmune disease. So, a typical first-round population.
The regimen tested was a combination of melatonin (5mg), strontium citrate, Vitamin D3 & Vitamin K2 (MSDK) Dosages of the other 3 not disclosed in the report
It yielded impressive results in the 11 people who completed the trial, compared to the 11 on placebo, and they stated, "... In our study, osteopenic women taking MSDK for one year had a significant improvement in their left femoral neck and lumbar spine BMD and demonstrated a lower risk for a major osteoporotic fracture risk compared to women taking placebo. This is consistent with previous studies that demonstrate an increased BMD using melatonin alone [12], strontium alone [13, 14] or combination vitamin D3 and vitamin K2 [17, 18] or combination strontium citrate, vitamins K2 and D3 [20]. MSDK was found to be less effective in improving hip BMD, perhaps due to the kinetics of bone remodeling in long vs. flat bones [52]"

My takeaway:
There should be Phase 2 & 3 clinical studies to evaluate effectiveness in typical populations and those who already have osteoporosis. Also a follow-up after 5 years of supplementation to demonstrate long-term efficacy.
We need to be careful about "grabbing onto" hope based on small studies, and taking supplements in different combinations and concentrations than are tested. We also need to know if they are effective when other conditions/medications enter the mix. And whether they are safe and effective long-term.

I don't have time right now, but will look at the COMB study on a different day.
Sue