The biotech version of David vs. Goliath just got more interesting, with the $3.7-billion-market-cap Mirati Therapeutics (MRTX) posting data this week for its KRAS inhibitor MRTX849 suggesting it can be competitive with AMG 510 from Amgen (AMGN 1.40%), which weighs in at a market cap of $126 million.

You can't make firm predictions on drugs from two different uncontrolled clinical trials, especially with low numbers of patients, but qualitatively, MRTX849 looks like it can stack up against AMG 510.

Here's how Mirati's data presented this week at the 2019 AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics stacks up against Amgen's data from the European Society for Medical Oncology late last month.

Cancer Type

MRTX849 Patients With Partial Responses

AMG 510 Patients With Partial Responses

Non-small-cell lung cancer

3/5 (60%)

7/13 (54%)

Colorectal cancer

1/2 (50%)

1/12 (8%)

Data source: company press releases. Data is from highest dose of both drugs.

With only five non-small-cell lung cancer patients tested at the highest dose with MRTX849, the only real conclusion investors can draw is that MRTX849 is in the ballpark with AMG 510.

The colorectal cancer data is even harder to say anything about. Is MRTX849 really helping 50% of patients or did Mirati Therapeutics get lucky finding one responder out of two? It's impossible to say, since small numbers are often inaccurate; Amgen, for instance, initially reported a 100% responder rate for three lung cancer patients, and now it's sitting at 54% with 17 patients tested.

One interesting tidbit that should give Mirati's investors hope: One lung cancer patient and one colorectal cancer patient saw their tumors shrink further from the first scan to the second scan, suggesting MRTX849 might have better durability -- again with the caveat that it's based on a low number of patients.

Sometimes safety can differentiate drugs when efficacy can't, but the safety profiles for the drugs appear similar and don't point to a clear winner. Mirati noted that the maximum tolerated dose hasn't been established yet, so the efficacy data could get better as long as a higher dose doesn't make side effects intolerable.

Doctor looking at a chest x-ray

Image source: Getty Images.

Mirati's staff and sling: combination treatments

If the efficacy and safety data ultimately end up being similar, Mirati will be at a disadvantage, given Amgen's commercial might.

But Mirati may be able to take down its Goliath with a little help from some friends.

Since MRTX849 and AMG 510 aren't a cure, they're likely to eventually be used in combination with other drugs in the hope that the combination can be additive, at the very least, and hopefully synergistic -- that is, the efficacy is better than the sum of the drugs individually -- as one drug weakens the tumor cell and the other kills it.

As a smaller player, Mirati could have an advantage in finding partners for MRTX849 because it has more to offer to larger pharmaceutical companies than Amgen. For example, if an initial partnership is successful, Mirati may be more likely to license the European rights to the drug to its new partner, while Amgen doesn't need an international partner. And with inside information about the how effective MRTX849 is, the large pharma partner could have an advantage if it chose to eventually acquire Mirati.

Long road

Investors should keep in mind we're only in round one of a long battle. As the number of patients increase, it'll be easier to see which drug has an advantage of if they're truly equal. Ultimately, any differentiation that emerges may not be apparent until the drugs are tested in combinations, so investors should keep an eye on which partners each drugmaker is able to secure.