There are over a hundred potential coronavirus vaccines and treatments in various stages of development, but who has time to follow them all?

This summer, AstraZeneca (AZN -1.12%), Regeneron Pharmaceuticals (REGN -0.60%), and Pfizer (PFE 1.59%) and BioNTech (BNTX -2.45%) will run large, late-stage clinical trials with their respective candidates -- so it won't be too much longer before we know if they have what it takes to put an end to the COVID-19 pandemic.

On your list of companies with experimental new drugs to watch, these should be at the very top. Here's why.

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AstraZeneca: AZD1222

The University of Oxford's Jenner Institute originally developed this vaccine candidate, formerly known as ChAdOx1 nCoV-19, based on a previous vaccine candidate meant to stop the coronavirus responsible for Middle East Respiratory Syndrome (MERS).

This coronavirus vaccine candidate, which AstraZeneca licensed and renamed AZD1222, uses the same neutered shell of an adenovirus called ChAdOx1 to deliver sets of genetic instructions that produce copies of the spike protein found on SARS-CoV-2, the coronavirus responsible for COVID-19. Since ChAdOx1 MERS had already passed a phase 1 safety study with flying colors, regulators were quick to allow clinical trials with AZD1222.

In late June, volunteers in Brazil began receiving AZD1222 in a large phase 3 trial, and we'll know more about its chance of success soon. The medical journal The Lancet will publish phase 1 results for the first time on Monday, July 20; they should let us know if AZD1222 is safe, and whether it led to the production of antibodies that might stop SARS-CoV-2 from entering host cells.

If AZD1222 continues to impress, it might not be as profitable as investors expect. AstraZeneca has commitments to supply hundreds of millions of doses, but the company's also agreed to supply the vaccine at no profit during the pandemic.

Regeneron: REGN-COV2

REGN-COV2 is a cocktail of two antibodies that Regeneron chose because they appear to complement each other. Immune systems produce lots of different antibodies in response to invading viruses, and choosing the most important ones to build a treatment around isn't easy.

All biotechnology companies claim their technology selects ideal new drug candidates before moving them into costly clinical trials. Unlike the vast majority of its biotech peers, though, Regeneron has a highly successful track record in this regard.

Regeneron's recent successes include an antibody cocktail that significantly reduced mortality rates for Ebola patients; the company used the same technique to develop REGN-COV2 as a potential COVID-19 treatment and temporary prophylactic for people at high risk of infection. In June, Regeneron began clinical trials for REGN-COV2 as a treatment, and in July as a preventative measure.

If REGN-COV2 can show a significant mortality benefit in the treatment setting, it will quickly replace Gilead Sciences' (GILD -1.74%) remdesivir as standard care for patients with severe cases of COVID-19. Sales of remdesivir -- priced at around $3,120 for a 5-day course of treatment -- are expected to reach around $2 billion this year, even though it didn't appear to reduce patients' risk of death from COVID-19. Of course, sales of REGN-COV2 could climb much higher if it becomes standard treatment for moderately affected COVID-19 patients as well.

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Pfizer and BioNTech: BNT162

Rather than advance just one candidate, Pfizer and the German company BioNTech are working together to test four related vaccine candidates. The different candidates within the BNT162 program deliver strands of messenger RNA (mRNA) that cause human cells to produce slightly different portions of SARS-CoV-2.

The two most advanced candidates from the BNT162 program, BNT162b1 and BNT162b2, recently received a fast-track designation from the Food and Drug Administration that could expedite the development and review process. Pfizer and Biontech will enroll up to 30,000 patients in a phase 3 study that could begin before the end of July.

The BNT162 program is well behind AZD1222, but taking four shots at the goal instead of just one might give it a better chance to succeed.

Play it safe

If you're looking for drugmaker stocks to buy, it's probably best to stick with companies that don't need their coronavirus programs to succeed in order to earn a profit for their shareholders. AstraZeneca, Regeneron, and Pfizer are well-established drugmakers with steady profits that will continue to flow even if their efforts to tackle COVID-19 completely flop.

Biontech is still a clinical-stage biotech with no products on the market, and BNT162 will be its first new drug program to reach phase 3 clinical trials. If it isn't a roaring success, shares of the risky biotech stock could fall hard.