Originally Published: 29 MAR 22 06:38 ET

Updated: 29 MAR 22 10:03 ET

By Parija Kavilanz, CNN Business

(CNN) -- Russia's refusal to rule out nuclear war has put the world in an unsettling reality: The unthinkable is suddenly a possibility -- if extremely remote. One drugmaker, Partner Therapeutics, isn't waiting to take action.

The company said it is helping to ramp up supply in Europe of Leukine, a drug to treat acute radiation syndrome (ARS), or radiation sickness from exposure to high dose radiation during a nuclear emergency.

Leukine is more widely and consistently used to reduce the incidence of severe and life-threatening infections in cancer patients undergoing chemotherapy as part of their treatment.

But the injectable medication can also be administered as a life-saving measure for patients exposed to dangerous levels of radiation outside of medical treatment: The drug can increase the chances of survivability if given in the critical 48 to 96 hours after initial exposure to a high dose of radiation from a nuclear blast or nuclear fallout.

Leukine isn't the only drug to treat acute radiation exposure in the United States. Three other drugs are approved by the Food and Drug Administration for this purpose: Amgen's Neupogen, Neulasta, and NPlate. Amgen did not respond to requests for comment about whether the company is increasing supplies of its acute radiation exposure treatment drugs.

Partner Therapeutics, has been closely monitoring the ongoing destruction and destabilization in Ukraine and the heightened vulnerability of Ukraine's nuclear power plants to a Russian attack. The company has been in contact with the World Health Organization and other NGOs to inform them about the drug.

"We knew in this situation we can't directly contact the government of Ukraine. So we've reached to WHO to offer the drug on a humanitarian basis if it's needed," said John McManus, Partner Therapeutics' chief business officer. "There's a small window to treat people after a nuclear event. So our outreach is about informing, preparedness and awareness of this drug should it become necessary."

But Leukine (whose generic name is sargramostim) is not currently approved for use in Europe to treat acute radiation syndrome. McManus said Europe's drug regulator, The European Medicines Agency (EMA), would typically refer to the WHO and the International Atomic Energy Agency's guidelines on treatments for ARS in the event of an emergency.

The IAEA in a 2020 publication titled "Medical Management of Radiation Injuries," referenced sargramostim as a treatment for radiation emergencies in adults.

Who's behind Leukine?

Based in Lexington, Massachusetts, Partner Therapeutics was founded in 2017 as a privately held biotech company with expertise in oncology and specializing in research and development of treatments for infectious diseases, including Covid-19. It manufactures Leukine at a plant in Lynnwood, Washington, that employs 145 people. The company doesn't disclose annual revenue.

In 2018, it acquired the global rights from French pharmaceutical giant Sanofi to manufacture and sell Leukine.

On March 24, one of Partner Therapeutics international distributors —Tanner Pharma Group — said in a press release that it has partnered with the drugmaker to significantly increase the drug's inventory in Europe in response to the war in Ukraine and the "escalating potential for incidents that could require rapid deployment of medical interventions to treat radiation or chemical exposure."

Ramping up supply

In the event of a nuclear attack, having immediate access to Leukine will be critical to save lives. "Being prepared is key," said McManus.

McManus noted Leukine has never been distributed widely.

Most hospitals in the US maintain some supply of radiation exposure treatment drugs like Leukine, which is a prescription medication and is given by medical professionals to patients, said Dr. Nelson Chao, professor of medicine and immunology and chief of the division of cellular therapy and bone marrow transplant at Duke University.

In an emergency situation, such as a nuclear attack, he said first responders would quickly administer the drug to as many people as possible who've encountered extreme radiation exposure.

"Hopefully that would be within 24 hours," said Chao who is also a member of the Radiation Injury Treatment Network, a national network of medical centers with expertise managing acute radiation syndrome following a mass casualty disaster involving radiological, nuclear, or chemical agents.

"In the event of acute radiation exposure, illness is determined by extent of exposure to radiation dose and time," said Chao.

But Leukine is no catch-all. For people whose exposure is in the most severe range of the radiation hazard scale as determined by the Centers for Disease Control and Prevention (CDC), Chao said treatment with Leukine or any other medication or treatment won't save lives.

"These treatments do work to increase chances of survivability but only for certain level of radiation exposure where the level of toxicity and trauma isn't extreme following a nuclear event," he said, adding that Leukine and its competing drugs also won't treat other side effects of radiation exposure that could occur.

While Chao said he's not aware of US hospitals stocking up on more Leukine, Neopogen or the other drugs, he said he's directly aware of his counterparts in Ukraine who want to get these medications as quickly as possible. "There is a lot of demand [in Ukraine] right now for them," he said.

How it works

Leukine was developed to help in the recovery of white blood cells following chemotherapy or radiation therapy.

Acute exposure to high doses of radiation can damage a person's bone marrow and lead to a mild, moderate, or severe loss in blood cell production. White blood cells are essential for the proper functioning of the body's immune system and to fight off infections.

Acute exposure to high doses of radiation have also occurred outside of a medical setting. Leukine was used to treat victims of the Chernobyl accident in Ukraine in 1986 and Japan's Tokaimura nuclear accident 1999, said McManus.

On March 29, 2018, the FDA approved Leukine to treat acute radiation syndrome in the event of a radiological or nuclear emergency. The agency said Leukine was found to increase survival when administered up to 48 hours after total body irradiation at doses expected to be potentially life threatening within the first few weeks after exposure. The government's approval of Leukine was on the basis of animal studies.

"Leukine has shown it can mitigate radiation illness and improve chances of survival when administered up to 96 hours after exposure," said Dr. Isabel Lauren Jackson, a radiation oncology research scientist and an associate professor of radiation oncology at the University of Maryland School of Medicine. Jackson advises Partner Therapeutics and US government agencies on radiation countermeasures.

"The type of weapon that has been mentioned in the news is a tactical nuclear warhead or low yield nuclear weapon. In a nuclear attack, people will be at risk for radiation exposure from the blast itself or from fallout," said Jackson.

People within 1 mile of a blast would be at greatest risk for exposure to radiation doses that could cause acute radiation sickness from the blast itself and anyone within 10 miles downwind of the blast would be in the wider dangerous radiation zone, she said.

Potassium iodide vs. Leukine

Demand for another radiation protection measure -- potassium iodide pills -- has jumped in recent weeks as anxiety grows over the looming threat of use of nuclear weapons in Ukraine, which would pose a risk of radioactive iodine (or radioiodine) being released. It can be breathed into lungs, and it can contaminate water, soil, plants and animals closest to ground zero.

If ingested or inhaled, radioactive iodine can harm the thyroid, a butterfly-shaped gland in the front of the neck that produces many of the hormones that regulate the body and increase the risk of thyroid cancer, according to the CDC.

When used as directed, potassium iodide in liquid or pill form can quickly saturate the thyroid gland and prevent it from absorbing radioactive iodine.

Jackson said potassium iodide, which consumers can buy directly, doesn't treat acute radiation illness.

The US government has maintained a stockpile of Leukine since 2013 for potential use in a radiation emergency and bought additional supply in 2016 and 2019, McManus said.

He declined to say if the government has increased its supply in recent weeks, coinciding with Russia's invasion of Ukraine but said the company is focused on helping build up inventory of Leukine in Europe should it be immediately needed for use in 24 hours.

Partner Therapeutics continues to research Leukine's potential in treating other diseases as well.

During the pandemic, it initiated studies involving hundreds of patients and supported by the US Department of Defense, to evaluate the role of Leukine in reducing progression of the disease and the need for hospitalization in Covid-19 patients.

The drugmaker is preparing to submit those findings to the FDA.