Newbornscreening SMA – From Pilot Project to Nationwide Screening in Germany

INTRODUCTION

The aim of newborn screening (NBS) is to diagnose diseases that lead to severe deficits if left untreated, preferably at a pre-symptomatic stage. Half a century ago, Wilson and Jungner defined criteria for which disease could be included in NBS programs [1]. While metabolic and endocrine disorders initially used to be the focus of newborn screening, the spectrum has now expanded including other diseases such as SCID, cystic fibrosis, sickle cell disease and spinal muscular atrophy, reflecting increased therapeutic options. In the past, newborn screening was based exclusively on the determination of metabolites. Screening for spinal muscular atrophy was the first time a primarily genetic testing approach was applied.

5q13.2-associated spinal muscular atrophy (SMA-5q) is the most common neurodegenerative disorder in childhood and the leading genetic cause of death in early childhood. The disease is caused by a homozygous deletion of exon 7 of the SMN1 gene (MIM*600354) in more than 95% of cases [2]. This gene encodes the survival motor neuron (SMN) protein, which plays a central role in the development of the peripheral nervous system during late pregnancy and the first months of life. The lack of sufficient SMN protein leads to premature apoptosis of motor neurons. Less than 5% of patients show compound heterozygosity, with a combination of a deletion in exon 7 and an additional pathogenic sequence variant on the other allele. Humans carry a second, almost identical pseudogene called SMN2, which differs from SMN1 only by the exchange of five bases. One of these exchanges leads to altered splicing with a less likely inclusion of exon 7 resulting in a substantially decreased amount of fully functional SMN protein.

The SMN2 gene is currently the most important predictor and modifier of the course of the disease [3, 4].

In the meantime, 3 different targeted therapeutic approaches that can specifically increase SMN protein production are available. These are based on either gene replacement therapy (GRT) [5, 6] or splice-modification at the pre-mRNA level [7]. Use of GRT with onasemnogene-abeparvovec is in Germany restricted to patients with 2 or 3 copies of SMN2, nusinersen can be applied in any genetically proven 5q13.2 associated SMA and risdiplam can be used in children elder then 2 months. The onset of treatment is critical for clinical efficacy.

Both survival and motor skills differ markedly between children who are treated presymptomatically with nusinersen and children who receive therapy only after the onset of symptoms [7, 8]. Similar results were found in children treated with GRT [9].

For this reason, efforts are underway worldwide to include SMA in general newborn screening (NBS). In several countries corresponding pilot projects have started. In the USA and in some countries of the European Union (Germany, Norway, Belgium) newborn screening for SMA has already been included in the general screening guidelines.

Several methods for the detection of children with SMA-5q in newborn screening are now available. All are essentially based on the detection of a homozygous deletion of exon 7 in the SMN1 gene by a quantitative PCR reaction [10].

Beginning in 2018, pilot projects in parts of Germany clearly demonstrated the benefit of newborn screening for spinal muscular atrophy in more than 500,000 newborns screened [11, 12]. While in the pilot projects a single screening laboratory performed the newborn screening using its own well-established method and the notification and follow up care of the families was provided by three well connected centers, transition to a nationwide newborn screening program is supposed to bring some new challenges.

METHODS

Information on the patients including the time course of the individual steps up to the final diagnosis were assessed via an online survey (lime-survey) which was filled out by each neuromuscular center taking care of the children with suspected SMA. Findings were compared to the data of the pilot projects which have been published previously [12].

The project was approved by the university of Munich (LMU) local ethics committee (project no. 22-0549 KB and project no 18–269). Compliance with guidelines on human experimentation was assured.

RESULTS

DISCUSSION

In this paper, we present the experience gained in Germany during the transition from the pilot project of newborn screening for SMA to nationwide screening. When moving from a pilot project involving a strictly limited number of stakeholders, who are usually committed to the success of the project, to a nationwide screening with multiple stakeholders, some difficulties are to be expected. Regarding laboratory diagnostics, in Germany NBS is performed by 11 laboratories, which are free to choose the PCR methods used. Confirmatory diagnostics can also be performed by the laboratories cooperating with the respective local centers according to their own standards. Recent data has shown that estimating the SMN2 copy number in particular can be critical [14]. Organizational structures in the cooperation between neuromuscular centers, obstetric clinics and screening laboratories cannot be assumed to exist, since the previous NBS almost exclusively concerned metabolic and endocrine diseases.

It turns out that early involvement of all stakeholders in the field is necessary. Together with patient advocacy groups and professional organizations common criteria were defined. It was agreed that centers that should care for newborns with suspected spinal muscular atrophy in NBS should have several years of experience in the field of spinal muscular atrophy and should be able to offer all currently available therapies. Only in this way an open-ended consultation seems feasible.

A successful screening program requires that both parents and all professional partners are convinced of the benefits of the program. With respect to parents, there is concern that uncertainty about the use of data obtained from newborn screening may lead to unwillingness to participate in screening programs [15]. As we saw in the pilot projects, the fact of genetic screening does not affect parents’ willingness to screen [11]. Nevertheless, continued information to parents about the usefulness of newborn screening in a variety of lay media with the widest possible dissemination seems necessary. Especially the information that therapies are available, that an early diagnosis leads to a better therapeutic outcome is essential for the positive evaluation by parents. However, it can be assumed that for most parents it is not the information about the specific clinical picture that is decisive, but a general assessment of the benefits. In a study in Japan, 99% of the parents interviewed considered screening to be useful, although not a single respondent knew about the disease spinal muscular atrophy [16]. The approval rate for NBS in Germany is also in the range of 99% [17].

Especially at the beginning of nationwide NBS, lack of information about essential steps to take after receiving a suspicious finding and the nearest contact persons can lead to a delay in the process. This results in the need to provide necessary information and contacts on an easily accessible platform.

Patient information is a critical issue in any newborn screening program. Both the initial notification of patients of suspected SMA and the discussion of confirmation diagnostics requires both factual and communication skills. All experts involved in the selection of centers agreed that a dedicated team responsible for this process needs to be available. A similar model is being implemented in other countries [18].

In everyday life, parents generally look to the Internet as their first source of information. For this reason, we have also included brief information on newborn screening on the treatment center page. However, it has become apparent that, given the very diverse ethnic backgrounds of families, information must be available in as many languages as possible to meet the need for information. While comprehensive information about the clinical picture of SMA in all its variants can be found on the Internet, there is still a lack of sufficient information in layman’s terms about the special situation of children treated very early, possibly even pre-symptomatically.

In contrast to the pilot project, in which no false positive findings were observed, four children had false positive findings in the first two months after the start of nationwide screening. The findings were reported back to the screening laboratories and led to modifications in the technical procedure. Given the enormous psychological impact of a false positive result on the family, care must be taken to ensure that the number of false positives approaches zero [12, 19]. Figures such as 61% of suspicious results which could not be confirmed in a pilot project are definitely too high [20]. To improve the quality of NBS, both preanalytical and analytical problems need to be addressed. Especially in the initial phase of other NBS programs, a rather high number of false positive results was observed in some projects, which improved as SMA-NBS became more established. This clearly demonstrates the need for feedback between treatment centers and screening laboratories.

In the period after the initiation of nationwide SMA NBS one patient with a compound heterozygeous mutation was detected who was missed by the NBS. Due to the fact that NBS is not allowed to screen for heterozygeous carriers this cannot be avoided. A similar case was found in the Belgium NBS project [21]. It underlines the necessity to inform the neuropediatric community about this blind spot of the NBS and about the necessity to extend genetic testing to sequence analysis in cases with a heterozygeous mutation and a clinical suspicion of SMA as proposed by the treatment guidelines by Cure SMA working group [22]. Other patients who were not detected by the newborn screening have not been noticed so far. Of course, it must be mentioned that the observation period is still short and that any forms that may occur at a later stage may not yet be clinically conspicuous.

In general, the availability and timing of targeted therapy is one of the cornerstones of any successful SMA-NBS program. The lack of accepted reimbursement for therapy in presymptomatic children is one of the major obstacles in some countries [23]. Time to treatment is largely influenced by non-medical factors such as transport time for blood testing, time to obtain insurance, and time to approve required reimbursement for therapies, in addition to medical issues such as time for genetic confirmation of suspicious findings, elevated liver enzymes, or AAV antibodies [24]. Care must be taken to minimize the time necessary to complete the various steps before treatment can begin. Depending on the structures in place in different countries, the time to notify families of the suspicious finding varied from 8 to 11 days after birth. The median start of treatment in patients with 2 or 3 SMN2 copies varied from 19 days after birth in our pilot study to 34 days [19, 24]. Knowing that at the time of the first clinical examination, up to one third of patients already show the first symptoms of SMA [19, 25], shortening this period is an important goal. For this reason, it is important to follow all children diagnosed with SMA-NBS and to reanalyze from time to time the problems during the process from screening to initiation of treatment.

The results of the present study show that, with appropriate preparation, it is possible to extend newborn screening without a significant loss of speed or quality. Only the time until confirmation diagnostics and SMN2 copy number were available was slightly longer than in the pilot project. This clearly shows how important it is to establish a close cooperation between molecular genetics and treatment centers at an early stage. Experiences from other programs show that these times can be further shortened with longer duration of the screening program and thus better-established procedures [21].

SMN2 copy number is generally considered a major modifier of disease severity and response to therapy [26]. Quantification is thus considered crucial for the selection of therapeutic options. In Germany, gene replacement therapy is only available for SMA patients with 2 and 3 SMN2 copies. Risdiplam is so far in Europe only approved for children older than 2 months, whereas nusinersen is approved for the entire spectrum of 5q-associated SMA. As our data show, a timely determination of SMN2 copy number is feasible if follow-up is performed by centers where established diagnostic structures exist. In the children included in nationwide NBS in Germany, this was predominantly done by certified neuromuscular centers. This highlights the need for pre-selection of follow-up centers.

While at the beginning of the pilot project a large uncertainty regarding the outcome in early treated spinal muscular atrophy complicated the counseling of parents, data are now available from several centers that allow a better estimation of the prognosis in early therapy [25]. While the prognosis for children with 3 SMN2 copies can be considered very good with timely treatment, a somewhat worse outcome for children with 2 SMN2 copies, however, must also be discussed with the parents. Corresponding data can be found in pilot studies as well as in clinical trials with presymptomatic patients [8].

In our study, most parents of children with 2 or 3 copies of the SMN2 gene were in favor of treatment with onasemnogene abeparvovec. Similar experiences have been reported by other research groups [24, 27]. However, a proportion of parents prefer RNA-based therapy mainly because of what they perceive as the unclear risk of gene replacement therapy. The lack of timely cost coverage by the health insurance is another reason that leads to a change of the therapy decision in individual cases. From our point of view, it seems important that parents are informed as objectively as possible about the benefits and risks of the individual therapeutic strategies.

Based on current data, the timing of treatment initiation is much more important than the choice of one of the targeted drugs [12, 28, 29]. For this reason, it is reasonable to perform SMA-NBS even at a time when not all treatment options are available.

In the case with 1 SMN2 copy, the decision was made to choose a purely palliative path. Overall, the indication of disease-modifying therapy in this particular situation is seen as problematic even if lesser progress is possible in individual cases [30, 31]. For ethical considerations, a palliative pathway is preferred by some authors. In this difficult situation, it is useful to allow a broader opinion to be formed through close interaction between neuromuscular centers.

Two of these were premature infants who did not yet meet the formal criteria for gene replacement therapy. The main problem in this situation is the knowledge that, on the one hand, progressive loss of motor neurons can occur before the calculated date of birth and, on the other hand, the safety profile of all three available substances is not sufficiently known for premature infants. In the meantime, it has been suggested to start the therapy at the latest at the 37th week of gestation [32].

In children with 4 SMN2 copies, a majority of the participating centers decided together with the parents to start therapy as early as suggested by the recommendations of the American ad-hoc committee [33, 34]. The discussion about this group is still ongoing. However, the fact that newborn screening has not led to an increase in the incidence of SMA compared with known figures in the German population [35] suggests that most children in this group will develop the disease, i.e. the number of long-term asymptomatic patients will be vanishingly small.

There is no generally accepted opinion on which drug should be used in these patients: In contrast to the U.S., onasemnogen abeparvovac is not approved in the EU and Canada for patients with ≥4 SMN2 copies because there are insufficient trial data on efficacy and safety for this patient population [36]. Given the less severe disease course expected in patients with ≥4 SMN2 copies, we believe further analysis of the benefit-risk ratio of gene replacement therapy in this patient group is warranted at this time.

In summary, our data confirms the possibility to expand a genetic NBS from a small, well defined pilot group to nationwide implementation with no loss of speed and quality.

CONFLICTS OF INTEREST

Becker, M.: owner of a commercial entitiy (Labor Becker, Munich, Germany)

Blaschek, A.: speaker honorarium Roche

Brockow, I.: nothing to declare

Burggraf, S.: nothing to declare

Cirak, S.: scientific advisory board Novartis gene therapy

Durner, J.: nothing to declare

Eggermann, K.: nothing to declare

Flotats-Bastardas, M.: scientific advisory board for Biogen, Avexis, Roche. Travel expenses from Biogen. Speaker fees from Avexis.

Friese J: scientific advisory board Novartis gene therapy

Gläser, D.: nothing to declare

Hagen,v.d. M.: member of a scientific advisory board for Avexis, Biogen, Novartis, Pfizer, Roche and Sarepta and received travel expenses and speaker fees from Biogen, Avexis, PTC, Pfizer, Roche, Sarepta

Hahn, A.: scientific advisory board for Biogen, Novartis Gene therapies and speaker fees from Biogen, Novartis Gene Therapies, PTC and Sanofi-Aventis

Hannibal, I.: nothing to declare

Hartmann, H.: nothing to declare

Horber, V-: participated in workshops and received compensation for advisory boards from Novartis and Biogen

Illsinger, S.: scientific Advisory board Novartis

Johannssen, J.: scientific advisory board participation and/or lectures and/or manuscript writing from Avexis/Novartis, Biogen, Roche, PTC, Pfizer and Sarepta

Kirschner, J.: Received honoraria for consultancy/educational activities and clinical research from Biogen, Novartis, Roche and ScholarRock.

Köhler, C.: honoraria for lectures from PTC, Biogen, Roche, Sanofi-Genzyme

Kölbel, H.: scientific advisory board for Novartis and received travel expenses and speaker fees from Biogen and Sanofi-Aventis

Moers von, A.: nothing to declare

Müller, Ch.: nothing to declare

Müller-Felber, W.: scientific advisory board for Biogen, Novartis, PTC, Sarepta, Sanofi-Aventis, Roche and received travel expenses and speaker fees from Biogen, Novartis, PTC, Roche, Sarepta and Sanofi-Aventis

Nennstiel, U.: nothing to declare

Olgemöller, B.: nothing to declare

Pechmann, A.: advisory boards and training activities, and research grants from Novartis and Biogen

Röschinger, W.: nothing to declare

Schara, U.: scientific advisory board Novartis, Roche and Biogen

Schreiber, G.: speaker fees from Novartis

Schwartz, O.: scientific advisory board for Avexis and received travel expenses and speaker fees from Biogen

Trollmann, R.: scientific advisory board for PTC and Biogen. Speaker fees from Biogen, Novartis, PTC.

Vill, K.: speaker fees from Biogen.

Weiss, C.: Personal and/or institutional fees for Advisory Boards and presentations from Novartis, Roche and Biogen

Winter, B.: Speaker fees and Advisory Boards from Novartis, Biogen and Roche

Wirth, B.: received travel expenses and speaker fees from Biogen and Avexis/Novartis

Ziegler, A.: scientific advisory board for Biogen, Avexis, PTC, Sarepta, Novartis Gene Therapies, Roche and Pfizer and received travel expenses and speaker fees from Biogen, Avexis, Novartis Gene Therapies, PTC, Roche, Sarepta and Pfizer

AUTHOR’S CONTRIBUTION

Wolfgang Müller-Felber, Astrid Blaschek and Katharina Vill conceptualized and designed the clinical study, co-drafted the initial manuscript, collected clinical data, and reviewed and revised the manuscript.

Oliver Schwartz, Uta Nennstiel, Inken Brockow, Heike Kölbel, Christine Müller, Iris Hannibal, Ulrike Schara, Arpad von Moers, Regina Trollmann, Jessika Johannssen, Andreas Ziegler, Sebahattin Cirak, Andreas Hahn, Maja von der Hagen, Claudia Weiss, Gudrun Schreiber, Marina Flotats-Bastardas, Hans Hartmann, Sabine Illsinger, Astrid Pechmann, Veronka Horber, Jan Kirschner, Cornelia Köhler collected clinical data and reviewed the manuscript.

Siegfried Burggraf, Wulf Röschinger, Marc Becker, Jürgen Durner,Bernd Olgemöller developed the NBS method used in the pilot projects.

Dieter Gläser, Brunhilde Wirth and Katja Eggermann performed the genetic confirmation and the SMN2 copy number determination and reviewed the manuscript.

All authors approved the final manuscript as submitted and agreed to be accountable for all aspects of the work.