English to Italian Medical Chemistry; Chem Sci/Eng Improved modalities for the treatment of degenerative diseases of the retina

Si tratta del brevetto Improved modalities for the treatment of degenerative diseases of the retina.
Nella parte dedicata a RPE defects in Retinitis Pigmentosa trovo:
Two gene defects that case autosomal recessive RP have been found in genes expressed exclusively in RPE: one is due to an RPE protein involved in vitamin A metabolism (cis retinaldehyde binding protein), a second involves another protein unique to RPE, RPE65.
Once rejection is conquered, both of these forms of RP should be treatable immediately by RPE transplantation.

Non trovo una soluzione soddisfacente e non capisco se forse manca una parola prima di cis.
Grazie mille.