Right now, many U.S. hospitals are stretched to the limit trying to help people battling serious cases of COVID-19. But as traumatic as this experience still is for patients and their loved ones, the chances of surviving COVID-19 have in fact significantly improved in the year since the start of the pandemic.
This improvement stems from several factors, including the FDA’s emergency use authorization (EUA) of a number of therapies found to be safe and effective for COVID-19. These include drugs that you may have heard about on the news: remdesivir (an antiviral), dexamethasone (a steroid), and monoclonal antibodies from the companies Eli Lilly and Regeneron.
Yet the quest to save more lives from COVID-19 isn’t even close to being finished, and researchers continue to work intensively to develop new and better treatments. A leader in this critical effort is NIH’s Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) initiative, a public-private partnership involving 20 biopharmaceutical companies, academic experts, and multiple federal agencies.
ACTIV was founded last April to accelerate drug research that typically requires more than a decade of clinical ups and downs to develop a safe, effective therapy. And ACTIV has indeed moved at unprecedented speed since its launch. Cutting through the usual red tape and working with an intense sense of purpose, the partnership took a mere matter of weeks to set up its first four clinical trials. Beyond the agents mentioned above that have already been granted an EUA, ACTIV is testing 15 additional potential agents, with several of these already demonstrating promising results.
Here’s how ACTIV works. The program relies on four expert “working groups” with specific charges:
Preclinical Working Group: Shares standardized preclinical evaluation resources and accelerate testing of candidate therapies and vaccines for clinical trials.
Clinical Trial Capacity Working Group: Has developed and organized an inventory of clinical trial capacity that can serve as potential settings in which to implement effective COVID-19 clinical trials.
To give you just one example of how much these expert bodies have accomplished in record time, the Therapeutics Clinical Working Group got to work immediately evaluating some 400 candidate therapeutics using multiple publicly available information sources. These candidates included antivirals, host-targeted immune modulators, monoclonal antibodies (mAb), and symptomatic/supportive agents including anticoagulants. To follow up on even more new leads, the working group launched a COVID-19 Clinical & Preclinical Candidate Compound Portal, which remains open for submissions of therapeutic ideas and data.
All the candidate agents have been prioritized using rigorous scoring and assessment criteria. What’s more, the working group simultaneously developed master protocols appropriate for each of the drug classes selected and patient populations: outpatient, inpatient, or convalescent.
Through the coordinated efforts of all the working groups, here’s where we stand with the ACTIV trials:
ACTIV-1: A large-scale Phase 3 trial is enrolling hospitalized adults to test the safety and effectiveness of three medicines (cenicriviroc, abatacept, and infliximab). They are called immune modulators because they help to minimize the effects of an overactive immune response in some COVID-19 patients. This response, called a “cytokine storm,” can lead to acute respiratory distress syndrome, multiple organ failure, and other life-threatening complications.
ACTIV-2: A Phase 2/3 trial is enrolling adults with COVID-19 who are not hospitalized to evaluate the safety of multiple monoclonal antibodies (Lilly’s LY-CoV555, Brii Biosciences’s BRII-196 and BRII-198, and AstraZeneca’s AZD7442) used to block or neutralize the SARS-CoV-2 virus. The Lilly monoclonal antibody LY-CoV555 received an EUA for high risk non-hospitalized patients on November 9, 2020 and ACTIV-2 continued to test the agent in an open label study to further determine safety and efficacy in outpatients. Another arm of this trial has just started, testing inhaled, easy-to-administer interferon beta-1a treatment in adults with mild-to-moderate COVID-19 who are not hospitalized. An additional arm will test the drug camostat mesilate, a protease inhibitor that can block the TMPRSS2 host protein that is necessary for viral entry into human cells.
ACTIV-3: This Phase 3 trial is enrolling hospitalized adults with COVID-19. This study primarily aims to evaluate safety and to understand if monoclonal antibodies (AstraZeneca’s AZD7442, BRII-196 and BRII-198, and the VIR-7831 from GSK/Vir Biotechnology) and potentially other types of therapeutics can reduce time to recovery. It also aims to understand a treatment’s effect on extrapulmonary complications and respiratory dysfunction. Lilly’s monoclonal antibody LY-CoV555 was one of the first agents to be tested in this clinical trial and it was determined to not show the same benefits seen in outpatients. [Update: NIH-Sponsored ACTIV-3 Clinical Trial Closes Enrollment into Two Sub-Studies, March 4, 2021]
ACTIV-4: This trial aims to determine if various types of blood thinners, including apixaban, aspirin, and both unfractionated (UF) and low molecular weight (LMW) heparin, can treat adults diagnosed with COVID-19 and prevent life-threatening blood clots from forming. There are actually three Phase 3 trials included in ACTIV-4. One is enrolling people diagnosed with COVID-19 but who are not hospitalized; a second is enrolling patients who are hospitalized; and a third is enrolling people who are recovering from COVID-19. ACTIV-4 has already shown that full doses of heparin blood thinners are safe and effective for moderately ill hospitalized patients.
ACTIV-5: This is a Phase 2 trial testing newly identified agents that might have a major benefit to hospitalized patients with COVID-19, but that need further “proof of concept” testing before they move into a registrational Phase 3 trial. (In fact, another name for this trial is the “Big Effect Trial”.) It is testing medicines previously developed for other conditions that might be beneficial in treatment of COVID-19. The first two agents being tested are risankizumab (the result of a collaboration between Boehringer-Ingelheim), which is already FDA-approved to treat plaque psoriasis, and lenzilumab, which is under development by Humanigen to treat patients experiencing cytokine storm as part of cancer therapy.
In addition to trials conducted under the ACTIV partnership, NIH has prioritized and tested additional therapeutics in “ACTIV-associated trials.” These are NIH-funded, randomized, placebo-controlled clinical trials with one or more industry partners. Here’s a table with a comprehensive list.
Looking a bit further down the road, we also seek to develop orally administered drugs that would potentially block the replication ability of SARS-CoV-2, the coronavirus that causes COVID-19, in the earliest stages of infection. One goal would be to develop an antiviral medication for SARS-CoV-2 that acts similarly to oseltamivir phosphate (Tamiflu®), a drug used to shorten the course of the flu in people who’ve had symptoms for less than two days and to prevent the flu in asymptomatic people who may have been exposed to the influenza virus. Yet another major long-term effort of NIH and its partners will be to develop safe and effective antiviral medications that work against all coronaviruses, even those with variant genomes. (And, yes, such drugs might even cure the common cold!)
So, while our ACTIV partners and many other researchers around the globe continue to harness the power of science to end the devastating COVID-19 pandemic as soon as possible, we must also consider the lessons learned this past year, in order to prepare ourselves to respond more swiftly to future outbreaks of coronaviruses and other infectious disease threats. Our work is clearly a marathon, not a sprint.
As this long year enters its final month, there is good reason to look ahead to 2021 with optimism that the COVID-19 pandemic will finally be contained. The Food and Drug Administration is now reviewing the clinical trial data of the Pfizer and Moderna vaccines to ensure their safety and efficacy. If all goes well, emergency use authorization could come very soon, allowing immunizations to begin.
Work also continues on developing better therapeutics against SARS-CoV-2, the novel coronavirus that causes COVID-19. Though we’ve learned a great deal about this coronavirus in a short time, structural biologists continue to produce more detailed images that reveal more precisely where and how to target SARS-CoV-2. This research often involves neutralizing antibodies that circulate in the blood of most people who’ve recovered from COVID-19. The study of such antibodies and how they interact with SARS-CoV-2 offers critical biological clues into how to treat and prevent COVID-19.
A recent study in the journal Nature brings more progress, providing the most in-depth analysis yet of how human neutralizing antibodies physically grip SARS-CoV-2 to block it from binding to our cells . To conduct this analysis, a team of NIH-supported structural biologists, led by postdoc Christopher Barnes and Pamela Björkman, California Institute of Technology, Pasadena, used the power of cryo-electron microscopy (cryo-EM) to capture complex molecular interactions at near-atomic scale.
People infected with SARS-CoV-2 (or any foreign substance, for that matter) generate thousands of different versions of attack antibodies. Some of these antibodies are very good at sticking to the coronavirus, while others attach only loosely. Barnes used cryo-EM to capture highly intricate pictures of eight different human neutralizing antibodies bound tightly to SARS-CoV-2. Each of these antibodies, which had been isolated from patients a few weeks after they developed symptoms of COVID-19, had been shown in lab tests to be highly effective at blocking infection.
The researchers mapped all physical interactions between several human neutralizing antibodies and SARS-CoV-2’s spike protein that stud its surface. The virus uses these spiky extensions to infect a human cell by grabbing on to the angiotensin-converting enzyme 2 (ACE2) receptor. The molecular encounter between the coronavirus and ACE2 takes place via one or more of a trio of three protein domains, called receptor-binding domains (RBDs), that jut out from its spikes. RBDs flap up and down in the fluid surrounding cells, “reaching up” to touch and enter, or “laying down” to hide from an infected person’s antibodies and immune cells. Only an “up” RBD can attach to ACE2 and get into a cell.
Taken together with other structural information known about SARS-CoV-2, Barnes’ cryo-EM snapshots revealed four different types of shapes, or classes, of antibody-spike combinations. These high-resolution molecular views show that human neutralizing antibodies interact in many different ways with SARS-CoV-2: blocking access to either one or more RBDs in their “up” or “down” positions.
These results tell us a number of things, including underscoring why strategies that combine multiple types of antibodies in an “antibody cocktail” might likely offer broader protection against infection than using just a single type of antibody. Indeed, that approach is currently being tested in patients with COVID-19.
The findings also provide a molecular guide for custom-designing synthetic antibodies in the lab to foil SARS-CoV-2. As one example, Barnes and his team observed that one antibody completely locked all three RBDs into closed (“down”) positions. As you might imagine, scientists might want to copy that antibody type when designing an antibody-based drug or vaccine.
It is tragic that hundreds of thousands of people have died from this terrible new disease. Yet the immune system helps most to recover. Learning as much as we possibly can from those individuals who’ve been infected and returned to health should help us understand how to heal others who develop COVID-19, as well as inform precision design of additional vaccines that are molecularly targeted to this new foe.
While we look forward to the arrival of COVID-19 vaccines and their broad distribution in 2021, each of us needs to remember to practice the three W’s: Wear a mask. Watch your distance (stay 6 feet apart). Wash your hands often. In parallel with everyone adopting these critical public health measures, the scientific community is working harder than ever to meet this moment, doing everything possible to develop safe and effective ways of treating and preventing COVID-19.