MHRA Grants Promising Innovative Medicine Designation to Nirsevimab

  • Nirsevimab is an innovative monoclonal antibody in Phase 2 and Phase 3 trials for the prevention of respiratory syncytial virus (RSV) infections in healthy late preterm, term and high-risk infants1,2
  • RSV is a contagious virus, and the most common cause of severe lower respiratory tract infections (LRTI) in infants and young children, resulting in over 30,000 hospitalisations per year in the UK due to RSV-associated LRTIs for children under five years3
  • Promising Innovative Medicine (PIM) Designation was granted based on non-clinical and clinical data of nirsevimab in healthy preterm infants
  • Nirsevimab does not have a Marketing Authorisation (MA) in the UK for any indication


The Medicines and Healthcare Products Regulatory Agency (MHRA) has granted a Promising Innovative Medicine (PIM) Designation to nirsevimab, an extended half-life monoclonal antibody (mAb) being investigated as a passive immunisation for the prevention of lower respiratory tract infections (LRTI) caused by respiratory syncytial virus (RSV) in all infants in their first RSV season, from birth and up to 12 months of age; and children with chronic lung disease or with haemodynamically significant congenital heart disease in their second RSV season, up to 24 months of age.

PIM Designations are given to medicinal products that are likely to offer a major advantage for patients. For the MHRA to grant a PIM Designation, the product must meet each of the following three criteria:4

  • Criterion 1: The conditions should be life-threatening or seriously debilitating with high unmet need, meaning there is no method of treatment, diagnosis or prevention available, or existing methods have serious limitations
  • Criterion 2: The medicinal product is likely to offer major advantage over methods currently used in the UK. Preliminary evidence should be submitted based on both non-clinical and clinical data
  • Criterion 3: The potential adverse effects of the medicinal product are likely to be outweighed by the benefits, allowing for the reasonable expectation of a positive benefit risk balance

"RSV is a pervasive respiratory disease, yet no approved treatments or preventative options available to all infants currently exist. The MHRA’s PIM Designation indicates nirsevimab is a promising option to help combat this still unmet need,” said Ian Gray, Sanofi UK Medical Director. “This exciting milestone reflects our deep commitment to bringing a preventative option to all babies against this common and potentially severe respiratory virus.”

The PIM Designation was based on Phase 2b results of nirsevimab, which found a significant (70.1%; [95% CI: 52.3%-81.2%]) reduction in medically attended LRTI due to RSV in healthy preterm infants, compared to placebo. The results also showed nirsevimab achieved a 78.4% (95% CI: 51.9%-90.3%) relative reduction in the incidence of hospitalisations due to RSV LRTI in healthy preterm infants, compared to placebo.5 Nirsevimab had a tolerable safety profile, with no significant hypersensitivity reactions observed.5

About RSV

RSV, a common, contagious virus that infects the respiratory tract, is the leading cause of LRTI (such as bronchiolitis and pneumonia) in infants and young children. By two years of age, nearly all children have been infected by RSV at least once.6 RSV results in millions of hospitalisations globally and nearly 60,000 deaths in children under five years of age every year.7,8,9 Globally, in 2015, there were approximately 33 million cases of acute lower respiratory infections, causing more than three million hospitalisations in children under five years of age.7

In the UK, from 2007 to 2012, there were an estimated 33,000 hospitalisations a year on average due to RSV-associated LRTI for children under five years of age.3 In the UK, annual healthcare costs associated with RSV infection in children under five years of age are estimated at £50–57 million, with hospitalisation costs accounting for £37 million and GP consultation costs accounting for £16–19 million.10 Globally, in 2017, RSV-related direct medical costs – including hospital, outpatient and follow-up care – were estimated at €4.82 billion.11

About Nirsevimab

Nirsevimab is an extended half-life RSV mAb being developed for the prevention of LRTI caused by RSV currently being investigated for use in all infants in their first RSV season, from birth to up to 12 months of age; and children with chronic lung disease or with haemodynamically significant congenital heart disease in their second RSV season, up to 24 months of age.

Nirsevimab is a passive immunisation, whereby an antibody is given intramuscularly (IM) to an infant to help prevent RSV, unlike active immunisation, in which a person’s immune system is activated to produce antibodies to a pathogen to prevent or fight infection.12 Passive immunisation has the potential to offer immediate protection.

In March 2017, AstraZeneca and Sanofi Pasteur announced an agreement to develop and commercialise nirsevimab jointly. Under the terms of the agreement, AstraZeneca leads all development activity through initial approvals and retains manufacturing activities and Sanofi Pasteur will lead commercialisation activities. In February 2019, AstraZeneca and Sanofi Pasteur’s nirsevimab received Breakthrough Therapy Designation from the US Food and Drug Administration and was granted access to the PRIority MEdicines (PRIME) scheme by the European Medicines Agency.

Nirsevimab Clinical Trials

The Phase 2b study was conducted at 164 sites in 23 countries. Healthy preterm infants of 29–35 weeks’ gestation were randomised (2:1) to receive a single intramuscular injection of nirsevimab or placebo. Between November 2016 and December 2017, 1,453 infants were randomised 2:1 to receive either nirsevimab or placebo at the RSV season start.5

In July 2019, Sanofi and AstraZeneca initiated pivotal Phase 3 and Phase 2/3 trials to measure the safety and efficacy of nirsevimab to prevent LRTI caused by RSV in full-term, healthy late preterm and high-risk babies.1,2 The trials are being conducted in more than 350 sites across Northern and Southern Hemispheres.2

About Sanofi

Sanofi is dedicated to supporting people through their health challenges. We are a global biopharmaceutical company focused on human health. We prevent illness with vaccines, provide innovative treatments to fight pain and ease suffering. We stand by the few who suffer from rare diseases and the millions with long-term chronic conditions.

With more than 100,000 people in 100 countries, Sanofi is transforming scientific innovation into healthcare solutions around the globe.

Sanofi, Empowering Life

Sanofi Forward-Looking Statements

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements are statements that are not historical facts. These statements include projections and estimates regarding the marketing and other potential of the product, or regarding potential future revenues from the product. Forward-looking statements are generally identified by the words “expects”, “anticipates”, “believes”, “intends”, “estimates”, “plans” and similar expressions. Although Sanofi’s management believes that the expectations reflected in such forward-looking statements are reasonable, investors are cautioned that forward-looking information and statements are subject to various risks and uncertainties, many of which are difficult to predict and generally beyond the control of Sanofi, that could cause actual results and developments to differ materially from those expressed in, or implied or projected by, the forward-looking information and statements. These risks and uncertainties include among other things, unexpected regulatory actions or delays, or government regulation generally, that could affect the availability or commercial potential of the product, the fact that product may not be commercially successful, the uncertainties inherent in research and development, including future clinical data and analysis of existing clinical data relating to the product, including post marketing, unexpected safety, quality or manufacturing issues, competition in general, risks associated with intellectual property and any related future litigation and the ultimate outcome of such litigation, and volatile economic and market conditions, and the impact that COVID-19 will have on us, our customers, suppliers, vendors, and other business partners, and the financial condition of any one of them, as well as on our employees and on the global economy as a whole. Any material effect of COVID-19 on any of the foregoing could also adversely impact us. This situation is changing rapidly and additional impacts may arise of which we are not currently aware and may exacerbate other previously identified risks. The risks and uncertainties also include the uncertainties discussed or identified in the public filings with the SEC and the AMF made by Sanofi, including those listed under “Risk Factors” and “Cautionary Statement Regarding Forward-Looking Statements” in Sanofi’s annual report on Form 20-F for the year ended December 31, 2019. Other than as required by applicable law, Sanofi does not undertake any obligation to update or revise any forward-looking information or statements.

1 A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended RSV LRTI in Healthy Late Preterm and Term Infants (MELODY). Available at: Accessed January 2021.

2 A Study to Evaluate the Safety of MEDI8897 for the Prevention of Medically Attended Respiratory Syncytial Virus (RSV) Lower Respiratory Track Infection (LRTI) in High-risk Children. Available at: Accessed January 2021.

3 Reeves, R, et al. Estimating the burden of respiratory syncytial virus (RSV) on respiratory hospital admissions in children less than five years of age in England, 2007‐2012. Influenza Other Respi Viruses (2017);11:122–129. DOI: 10.1111/irv.12443

4 MHRA. PIM Designation Guidance. Available at: Accessed January 2021.

5 Griffin MP, MD et al. Single Dose Nirsevimab for Prevention of RSV Disease in Preterm Infants. N Engl J Med 2020; 383:415-425. DOI: 10.1056/NEJMoa1913556

6 Green Book Chapter 27A Respiratory Syncytial Virus. Available at: Accessed January 2021

7 Glezen WP et al. Am J Dis Child. 1986;140(6):543-546

8 Shi T et al. Lancet. 2017;390(10098):946-958

9 Oxford Vaccines Group. What is RSV? Available at: Accessed January 2021

10 Cromer D, van Hoek AJ, Newall AT, Pollard AJ, Jit M. Burden of paediatric respiratory syncytial virus disease and potential effect of different immunisation strategies: a modelling and cost-effectiveness analysis for England. Lancet Public Health. 2017;2:e367-e74

11 Zhang S et al. J Infect Dis. 2020. doi: 10.1093/infdis/jiz683

12 Vaccines & Immunizations.” Centers for Disease Control and Prevention. August 18, 2017. Available at: Accessed January 2021

Date of preparation: January 2021
Document number: MAT-GB-2100200 (v1.0)


Media Relations Contact
Andrea Welch
Vaccines Communications Lead
+44 (0) 7725 765377


Media Relations Contact
Andrea Welch
Vaccines Communications Lead
+44 (0) 7725 765377