ASD concern

I have my four yr old sign recently diagnosed na may ASD, we'll start Occupational therapy for intervention. 4yrs old is not too late pa naman po for therapy? He can speak naman pero di nya kaya maghold ng long conversations and somwtimes minimal contact and di tumitingin ag tinatawah especially pag engaged s ginagawa nya. Pero in terms of academics nkakasabay nman sya so far. Has anybody here got same experience? Kmusta na po babies nyo or progress nila? TIA!