The emergence of new diseases presents a constant challenge to medical science, often leaving us without immediately available and proven effective treatment methods. Experiences with recent epidemics highlight the critical importance of a rapid scientific response. Researchers at the University of California, San Francisco (UCSF) have shown that crucial scientific research for finding drugs does not have to wait for a crisis situation to end, but can and should be conducted 전쟁currently with it. The mpox pandemic, formerly known as monkeypox, served as an important testing ground for such efforts.

During the global mpox epidemic in 2022, the United States recorded more than 20,000 cases of illness and nearly sixty deaths. The city of San Francisco was among the hardest-hit areas. Although the World Health Organization (WHO) lifted the Public Health Emergency of International Concern (PHEIC) status for mpox in May 2023, the disease continues to pose a health challenge in many parts of the world and requires ongoing surveillance and research.

Modes of transmission of the mpox virus

The mpox virus spreads primarily through close contact with an infected person. Transmission occurs when a healthy person comes into contact with skin lesions, body fluids (such as fluid from blisters, pus, or blood from lesions), or scabs of an infected person. The virus can also pass from person to person through respiratory droplets during prolonged face-to-face contact, although this route is considered less effective. Additionally, contaminated objects and surfaces, such as bedding, clothing, or towels used by an infected person, can be a source of infection. Vertical transmission, from mother to child during pregnancy or childbirth, is also possible.

During the 2022 epidemic, a significant increase in sexual transmission was observed, particularly among men who have sex with men. Although mpox is not classified exclusively as a sexually transmitted disease, close physical contact during sexual intercourse, including skin-to-skin contact with lesions, represents a high-risk situation for transmission.

Different virus strains and their characteristics

The mpox virus belongs to the genus Orthopoxvirus, which also includes the variola virus (smallpox). There are two main genetic groups, or clades, of the mpox virus: Clade I and Clade II. Historically, Clade I, which has predominantly circulated in Central Africa (e.g., the Democratic Republic of Congo) and East Africa, is associated with more severe forms of the disease and a higher mortality rate, which can reach up to 10%. On the other hand, Clade II, traditionally present in West Africa, usually causes a milder clinical picture. The global epidemic that began in 2022 was caused by a subtype of Clade II, known as Clade IIb, after it initially spread through Europe and then the United States. Understanding the differences between clades is crucial for risk assessment and the development of specific treatment and prevention strategies.

Symptomatology and clinical picture of mpox

Mpox can cause significant discomfort and is characterized by painful blisters and a rash that can lead to temporary or permanent skin disfigurement. Typical symptoms include fever, headache, muscle aches, back pain, exhaustion, and swollen lymph nodes, which is a characteristic sign that helps distinguish mpox from some other rash-inducing illnesses, such as chickenpox. The rash usually appears 1 to 3 days after the onset of fever, often starting on the face and then spreading to other parts of the body, including the palms and soles, oral mucosa, genitals, and eyes.

In most cases, mpox is a self-limiting disease, and symptoms resolve on their own within two to four weeks. The risk of a fatal outcome with Clade IIb, which caused the recent epidemic, is relatively low. However, the disease can take a more severe form and carry a risk of complications and death, especially in children, pregnant women, and individuals with weakened immune systems, particularly if they have not been vaccinated against smallpox (the smallpox vaccine provides some cross-protection against mpox).

The primary treatment for patients with mpox is focused on alleviating symptoms, such as controlling pain and fever, and preventing secondary bacterial infections of skin lesions. Adequate hydration and nutrition are also important for recovery.

Challenges and successes in conducting clinical trials during an epidemic

Historically, initiating clinical trials during outbreaks of infectious diseases has been a significant challenge due to the urgency of the situation, logistical hurdles, and ethical dilemmas. However, a team from the University of California, San Francisco (UCSF), led by Dr. Annie Luetkemeyer, head of the global clinical trials advancement unit (ACTG), managed to launch an international clinical trial relatively quickly. Dr. Luetkemeyer points out that the key to success lay in previously completed work and existing data on the safety and potential efficacy of the drug tecovirimat (also known as TPOXX) against the smallpox virus, a close relative of the mpox virus. The ability to rapidly initiate a clinical trial, within less than a year of the epidemic's onset, was crucial for obtaining scientific data in real-time.

During the 2022 epidemic, the U.S. Centers for Disease Control and Prevention (CDC) allowed doctors to prescribe tecovirimat to some patients under an expanded access program (investigational use), given the lack of approved treatments for mpox. Most doctors prescribed tecovirimat, an antiviral drug known to be effective against smallpox.

Results of the study on tecovirimat (TPOXX)

The clinical trial led by UCSF aimed to determine the actual efficacy of tecovirimat in treating mpox. The results showed that TPOXX is a safe and well-tolerated drug in patients with mpox. Unfortunately, the study did not show that the use of tecovirimat speeds up patients' recovery time or reduces the duration of symptoms compared to a placebo. One possible explanation for why TPOXX did not show the expected efficacy lies in the drug's pharmacokinetics – it is possible that the current dosing regimen or pharmaceutical form of the drug is not optimal for achieving a sufficient concentration of the drug at the site of mpox virus activity. Also, there is a possibility that tecovirimat would be more effective if administered in combination with another antiviral drug. Finally, the possibility cannot be ruled out that TPOXX, despite promising results from preclinical, animal studies on smallpox, is simply not a sufficiently effective drug specifically for mpox.

Interestingly, a parallel study, mostly among children in the Democratic Republic of Congo, where a different clade (Clade I) of the mpox virus circulates, reached very similar conclusions about the (in)efficacy of tecovirimat. These findings underscore the importance of rigorous clinical trials even for drugs that seem promising based on in vitro studies or efficacy against related viruses.

Equity and ethics in clinical trials: Inclusion of pregnant women and children

Pregnant women and children are often more susceptible to severe outcomes of infectious diseases, including mpox, due to the specifics of their immune systems. Despite this, these groups have historically often been excluded from the early stages of clinical trials for new drugs for precautionary reasons and fear of potential adverse effects. Such a practice, although guided by caution, leads to a lack of data on the safety and efficacy of drugs in these populations. Consequently, drug manufacturers cannot submit applications for approval of their drugs for use in these groups, meaning that pregnant women and children sometimes have to wait years for access to life-saving drugs that are available to the general population.

The trial conducted by UCSF was designed with the intention of overcoming these obstacles. Dr. Luetkemeyer explains: "Our trial was designed to allow the inclusion of pregnant women and children in an open-label arm of the study, along with patients who were very ill, because it was considered unethical to randomize individuals at high risk of poor outcomes to potentially receive a placebo."

Innovative clinical trial design

Randomized controlled trials (RCTs) are considered the "gold standard" in medical science. Randomization, which can be compared to flipping a coin to select teams, ensures that the group of participants receiving the investigational drug is comparable to the group not receiving it (or receiving a placebo). This ensures that all characteristics that could affect a person's susceptibility to the drug, such as genetics, sex, or age, are equally represented in both groups, minimizing bias.

The UCSF study maintained the principles of a randomized controlled trial but with an innovative approach that included three arms, only two of which were randomized. As Dr. Luetkemeyer clarifies: "We did not randomize pregnant women, children, those with severe mpox, or those with weakened immune systems because we understood they were at increased risk of severe illness." Instead, it was ensured that they were part of a third, "open-label" arm of the study. This approach allowed these vulnerable groups to receive the treatment that was considered the best available care at the time (in this case, tecovirimat, as it was available through expanded access programs), while simultaneously collecting valuable data that will help shape future treatments for them. The results from this open-label arm were taken into account when analyzing the overall findings of the study, ensuring scientific validity while adhering to ethical principles.

The search for new therapeutic options for mpox

Although tecovirimat did not prove to be a solution for faster recovery from mpox, research continues. One promising drug is brincidofovir, another antiviral drug approved for the treatment of smallpox. Laboratory tests (in vitro) have shown that brincidofovir has activity against the mpox virus. The Centers for Disease Control and Prevention (CDC) already allow doctors to prescribe brincidofovir to patients with severe forms of mpox, also under an investigational drug use program.

In addition to antiviral drugs, researchers are also exploring the potential of monoclonal antibodies. These are laboratory-produced antibodies designed to target specific antigens on the virus, similar to those developed and used to treat COVID-19. Monoclonal antibodies could offer passive immunization and help neutralize the virus in infected individuals.

The indispensable role of clinical trials in health emergencies

Clinical trials like the one conducted by UCSF for mpox are absolutely essential during disease outbreaks. They allow for a scientific assessment of whether promising, yet still investigational treatments, such as tecovirimat, are safe and effective. During the mpox epidemic, there was a high demand for tecovirimat through expanded access programs. However, without data from randomized controlled trials, its actual benefit could not be definitively determined. The UCSF study, along with research conducted in the Democratic Republic of Congo, answered this important question, showing, unfortunately, that TPOXX did not improve recovery time from mpox. Given these findings, the widespread use of TPOXX for this indication has not proven beneficial, and other treatment strategies need to be explored.

Ultimately, such trials provide the scientific basis for making informed treatment decisions and guide further research towards effective therapies for current and future epidemics. They are crucial for distinguishing real medical help from false hope, even under the pressure of a public health crisis.

Source: University of California