The Commissioner of the FDA, Scott Gottlieb, recently informed a US House Committee on Appropriations of the agency’s intention to expand its guidance documents on developing drugs in specific disease areas to increase the number of new medicines in these fields and focus on the most effective ways to improve safety and efficacy. Among the indications the FDA specifically wishes to support are rare pediatric cancers and pediatric HIV.
An FDA briefing document released on April 20, 2018 stated that: “Pediatric cancer drug development typically leverages adult cancer drug discovery but has lagged far behind development of cancer drugs for adults. To date, the Pediatric Research Equity Act (PREA) has not been an effective mechanism to support the development of drugs for pediatric cancers because the requirement for conduct of pediatric studies is linked to the indication sought in adults and most adult cancers occur rarely, if ever, in children.”
Rare cancers constitute fewer than 1 in 30 of all pediatric cancers. Some affect only children, such as pancreatoblastoma, malignant rhabdoid tumors, and melanotic neuroectodermal tumors of infancy. Oncological indications which only usually affect adults are also considered rare in children. These include cancers of the digestive system, adrenal gland, lung, and thyroid. Malignant rhabdoid tumors in particular are often aggressive and difficult to treat. Currently, these tumors are treated with a combination of chemotherapy drugs and surgery (if operable), which the intensity of can result in survivors facing arduous health issues. Recent research aims to understand the biological basis of rhabdoid tumors, including the role of genetic mutations in gene SMARCB1 which would help develop more effective treatment methods for pediatric patients. The aforementioned FDA Briefing Document outlines that molecularly targeted agents have recently “advanced the concept of precision medicine in oncology”. Genetic abnormalities can often differ between adult and pediatric cancers, meaning the line of investigation into specific molecular targets for pediatric patients is extremely valid. Interestingly, in terms of indications which usually only affect adults, childhood manifestations of these tumors tend to contain far fewer genetic alterations meaning researchers can hone in on mutations more clearly, whilst the genomes of adult tumors are scarred by many more mutations.
Recent sequencing efforts aiming to provide evidence of the difference in mutations between adult and childhood cancers, such as the work of St Jude Children’s Research Hospital in Memphis, TNT have analyzed large quantities of tumors and found more than 140 genes potentially driving growth. Of those, just 45% matched drivers of tumor growth in adult patients, supporting the notion that the development of a targeted gene sequencing panel specific to pediatric cancers would be beneficial.
Despite all of this, and as mentioned by the FDA Briefing Document, cancer research in children lags behind. This is largely due to the rare nature of pediatric cancers meaning fewer patients to enroll in research efforts, fewer tumors to analyze and sequence and less R&D investment overall. FDA emphasis upon guiding pediatric clinical investigations towards safe and effective therapies, combined with advances in understanding of the biological basis of childhood cancers, however, are positive steps in the right direction.
In terms of HIV in children, there are currently an estimated 2.1 m sufferers under the age of 15 worldwide. Those with access to treatment are given a combined antiretroviral therapy (ART) and treatment of specific comorbid malignancies/infections.
The infection in children is most commonly a result of mother-to-child infection, of which only 1%-2% occurs in neonates, the majority occurring during childbirth (blood transmission) or during breastfeeding. Most pediatric sufferers (and adult alike) live in low and middle-income countries, the most affected region being sub-Saharan Africa where many have no access to prevention, treatment or care.
World Health Organization guidelines estimate approximately 50% of children with HIV have access to life-saving treatments. There are many roadblocks to treatment for those without access, including distance to clinics, social stigma, lack of support for healthcare providers, and lack of medicines specific to pediatric patients. Whilst current ART treatments have proven effective, many are not child-friendly. Treatment for children aged under three in particular can be difficult due to difficulty swallowing pills and the unpleasant taste of liquid medicines.
In a similar way to pediatric cancers, treatment options for children with HIV lags behind. This may uniquely be in part because high-income countries have almost eliminated childhood HIV, therefore the commercial market is very small. Improved pediatric ART formulations at an affordable price are vitally important to our global community to ensure rapid and accessible treatment for those who require it. FDA emphasis on the treatment of pediatric HIV supports the President's Emergency Plan for AIDS Relief (PEPFAR), the US commitment to alleviate the burden and suffering caused by HIV/AIDS worldwide, and 90-90-90, the 2020 UNAIDS target. UNAIDS hopes that “by 2020, 90% of all people living with HIV will know their HIV status. By 2020, 90% of all people with diagnosed HIV infection will receive sustained antiretroviral therapy. By 2020, 90% of all people receiving antiretroviral therapy will have viral suppression”. Improved care of pediatric patients, particularly of those born carrying the virus, or those to which it is transmitted as babies, can only help achieve this goal and improve the lives of future generations.
Harris Dalrymple, PhD (Medicine), PhD (Law)
Executive Director of Scientific Affairs
Vice Chair, Center for Pediatric Clinical Development
PRA Health Sciences
FDA Briefing Document Relevant Molecular Targets in Pediatric Cancers: Applicability to Pediatric Therapeutic Investigations Required Under FDARA 2017 https://www.fda.gov/downloads/Drugs/NewsEvents/UCM603075.pdf
Macmillan – Rare cancers in children
SMARCB1-deficient Tumors of Childhood: A Practical Guide (Pediatric and Developmental Pathology) http://journals.sagepub.com/doi/abs/10.1177/1093526617749671
Virasami, A., Farndon, S. J., McDermott, U., Sebire, N. & Behjati, S. Lancet Oncol. 18, e237 (2017). https://www.nature.com/news/century-old-tumours-offer-rare-cancer-clues-1.21975
St Jude Childrens Research Hospital Division of Cancer Predisposition https://www.stjude.org/research/departments-divisions/oncology/cancer-predisposition.html
Children and HIV UNAIDS http://www.unaids.org/sites/default/files/media_asset/FactSheet_Children_en.pdf