Ronan Kanda, 16, died after being stabbed in Mount Road near his home in Lanesfield near Coseley on June 29.
An 18-year-old man has been arrested at an address in Birmingham on suspicion of murder on Wednesday morning and remains in custody while investigations continue.
Speaking of the latest arrest, Detective Inspector Ade George said: "This is another positive development in this enquiry but I'd still urge anyone who was driving in the area at the time to get in contact.
"We understand there were other vehicles on the road around the time and they may have dashcam footage of the attack or the minutes leading up to it.
"So if you were in the area last Wednesday evening, and haven't yet spoken to us, please get in touch."
It comes as a 20-year-old and two youths appeared in Wolverhampton crown court charged with the murder.
No pleas were made and all three defendants appeared by video link and spoke only to confirm their names and addresses.
Judge Michael Chambers QC set a trial date for April 24 next year and adjourned the case until September 19 for a plea and case management hearing.
Meanwhile, a 15-year-old boy and an 18-year-old man held earlier this week were released on police bail.
A spokesperson for West Midlands Police said: "You can contact us via Live Chat on our website west-midlands.police.ukor by calling 101. Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
"Please quote reference number 3854-290622."